Add documentation for Review Apps

## What does this MR do?

Add docs for review apps.

## What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23484

See merge request !6982

Improvements to Redis HA docs

Following https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6471

See merge request !7502

Refactor environments documentation

## What does this MR do?

Refactor environments docs.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/23484

See merge request !7107

Revert "Merge branch '22680-unlabel-limit-autocomplete-to-selected-items' into 'master'"

There were some issues with the initial implementation: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6796#note_18557076

This reverts https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6796

See merge request !7521

Stop environment when branch is deleted

## What does this MR do?

This MR adds a environment teardown service, that is called when user deletes a branch. This most often happens when merge requests is merged.

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing

## What are the relevant issue numbers?

Closes #23218

See merge request !7355

Remove ToC and fix headings in Markdown docs

See merge request !7523

Adds hash anchors to diff_files to make possible linking exact file in commit

Closes #24010

See merge request !7298

tests: Move rake assets:precompile and cloning gitlab-{shell,test} to the prepare stage

Related to #23034

See merge request !7512

Update the updated_at of a build while patching the trace

## What does this MR do?

Fixes build patching trace. It should update the `updated_at` field of a build to make sure it will not be removed by `stuck_ci_builds_worker`.

## Are there points in the code the reviewer needs to double check?

Construction of a test for the bug.

## Why was this MR needed?

Please read #22087 for a reference.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Fixes #22087

See merge request !7146

Added colored labels to related MR list.

## What does this MR do?
Added colored labels to related MR list.

## Are there points in the code the reviewer needs to double check?
Yes, I think haml can be better.

## Why was this MR needed?
There was an issue for this #21200 

## Screenshots (if relevant)
![Screen_Shot_2016-11-15_at_21.04.24](/uploads/b601f33f23cdc3318d01279e17deb096/Screen_Shot_2016-11-15_at_21.04.24.png)

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Fixes !21200

See merge request !7486

Check all namespaces on validation of new username.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/24519 and https://gitlab.com/gitlab-org/gitlab-ce/issues/24580

See merge request !7537

Allow sorting groups in API

Relates to #20013.

See merge request !7529

Support subscribing to group labels

https://gitlab.com/gitlab-org/gitlab-ce/issues/23586

See merge request !7215

Highlight first user autocomplete option

See merge request !7520

Change the slack notification comment link.

## What does this MR do?

Changes the link in Slack notifications for comments.

## What are the relevant issue numbers?

Closes #24107

See merge request !7498

bump rouge to 2.0.7

## What does this MR do?
Upgrades Rouge to 2.0.7 for various bugfixes.

## Are there points in the code the reviewer needs to double check?
See the Rouge changelog here: https://github.com/jneen/rouge/blob/v2.0.7/CHANGELOG.md

See merge request !7549

Resolve "Create a tab shortcut to jump directly to content"

## What does this MR do?
Adds accessibility shortcut to page, i.e. if user hits `tab` key right after the page is loaded and user has not interacted to any part of the page, the shortcut appears at top left corner of the page. Then, pressing `enter` (`spacebar` support is WIP) scrolls page to focus on content.

## Are there points in the code the reviewer needs to double check?
See if `id` attribute added to `.content` element (present in [_page.html.haml](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/views/layouts/_page.html.haml)) needs to be reviewed if it is correct approach or we already have an ID that shortcut can refer to.

## Why was this MR needed?
This feature is particularly useful for screen readers where user doesn't have to go through entire nav to reach content of page.

## Screenshots (if relevant)
![Screenshot_from_2016-11-17_17-59-22](/uploads/0eb0149f46bd35e9ce629e7a6533be53/Screenshot_from_2016-11-17_17-59-22.png)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #24057

See merge request !7533

Add placeholder in the color input inside the create new label popup

## What does this MR do?
Adds the missing placeholder  *"Assign custom color #FF0000"*  in the label creation popup ( example text for custom hex color).

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?
When creating a new label, the example text for custom hex color is missing

## Screenshots (if relevant)
Before
![before](/uploads/a3157414d59cea609118a7d711f9b9ee/before.png)

After
![Selection_051](/uploads/ca3e2089b40069e4cb6b7aa295b28cfc/Selection_051.png)

## Does this MR meet the acceptance criteria?

- [X] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [X] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
#24512 

See merge request !7492

Update "Supported web browsers" text

## What does this MR do?

Updates the `Supported web browsers` text in the installation docs.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

Slack discussion

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !7341

Improve importing of github pull requests

Closes #24072

See merge request !7241

Fix line numbers not matching up with code in Firefox.

Firefox has had broken line number alignment for a while now, if this is a bug with Firefox they don't seem to want to fix it since its been there from 46 through 49. This fixes it.

Before:

![Screen_Shot_2016-09-22_at_3.08.44_PM](/uploads/8bb65f40e44f738c0c375b0c8ef7dea6/Screen_Shot_2016-09-22_at_3.08.44_PM.png)

After:

![Screen_Shot_2016-09-22_at_3.09.10_PM](/uploads/9e537be56886569d8a82390f2b97c42b/Screen_Shot_2016-09-22_at_3.09.10_PM.png)

Fixes #20202.

Safari/Chrome work the same as before, Snippets seems to work fine still as well.

Page tested: http://localhost:3000/gitlab-org/gitlab-ce/blob/master/app/models/project.rb

cc: @annabeldunstone

See merge request !6485

Fixing the issue of visiting a project fork url giving 500 error when not signed…

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/24302

See merge request !7392

Allows to authorize chat user against GitLab.

This is needed for: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7438

See merge request !7450

Remove unused CI gems

See merge request !7522

Allow registering users where the username contains dots (.)

## What does this MR do?

- Allow registering users whose usernames contains dots `.`
- This can currently be done by registering with a username containing no dots, and then editing the username to have dots in the user's profile settings.

## Does this MR meet the acceptance criteria?

-  [#24276/!7500] Unable to register names with dot
    - [x]  Implementation
    - [x]  Tests
        - [x]  Added
        - [x]  [Passing](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7500/builds)
    - [x]  Meta
        - [x]  CHANGELOG entry created
        - [x]  Documentation created/updated
        - [x]  API support added
        - [x]  Branch has no merge conflicts with `master`
        - [x]  Squashed related commits together
    - [x]  Review
        - [x]  Endboss
            - [x]  Use `Gitlab::Regex::NAMESPACE_REGEX_STR` instead of a hardcoded pattern
            - [x]  Define `NAMESPACE_REGEX_STR` in terms of `NAMESPACE_REGEX_STR_JS`
    - [ ]  Wait for merge


## What are the relevant issue numbers?

- Closes #24276

See merge request !7500

Include author in assignee dropdown search

## What does this MR do?

Previously when you searched for the author in the assignee dropdown (if they aren't in the project) it did not actually include the author. This changes that so that when you search for the author it will correctly include the user.

## Screenshots (if relevant)

![Screen_Shot_2016-11-17_at_11.14.53](/uploads/5a13475d8ded459fd3b1ba6570897665/Screen_Shot_2016-11-17_at_11.14.53.png)

## What are the relevant issue numbers?

Closes #22905

See merge request !7526

Add changelog entry for 7251

See merge request !7543

Fix Admin Links to new Group does not respect Default Visibility

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/19981

See merge request !7560

More aggressively preload on merge request and issue index pages

See merge request !7564

Correct curl examples for archive and unarchive project API

[ci skip]

See merge request !7559

Pipelines page redesign

Closes #23637
![Screen_Shot_2016-11-15_at_1.36.34_PM](/uploads/edc6a58f00cca3e03ffd1689bd6eebd8/Screen_Shot_2016-11-15_at_1.36.34_PM.png)

See merge request !7487

Fix misaligned buttons on admin builds page

## What does this MR do?
Fix misaligned buttons on admin builds page

## Are there points in the code the reviewer needs to double check?
No

## Why was this MR needed?
Because buttons are misaligned.

## Screenshots (if relevant)
![fix-admin-ci-table](/uploads/49472f7a12f868556e1bf482c9f837c4/fix-admin-ci-table.gif)

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Fixes #24371

See merge request !7424

Add environment info to builds page

![Screen_Shot_2016-11-02_at_5.44.01_PM](/uploads/3443d9518997147d1e6f41830e3774ff/Screen_Shot_2016-11-02_at_5.44.01_PM.png)

Closes #23205

See merge request !7251

Pass correct tag target to post-receive hook when creating tag via UI

Fixes #24437

See merge request !7556

Remove title from skipped status svg

Closes #24617

See merge request !7570

Resolve "spec/lib/gitlab/backend/shell_spec.rb causes other specs to fail"

## What does this MR do?

It ensures we rely on `Gitlab::Shell`'s public API and not on its internal. Since `Gitlab::Shell` is caching the value of its token, the only way to get the correct token is to call `Gitlab::Shell.secret_token`, not to read the `Gitlab.config.gitlab_shell.secret_file` file!

Fixes #24599

See merge request !7557

add parsing support for incoming html email

## What does this MR do?
Fixes #18388 by adding support for parsing HTML email

## Are there points in the code the reviewer needs to double check?
The new class, Gitlab::Email::HTMLParser, which needs to translate the HTML content to text and also delete replies, as they are not necessarily in the correct format to be caught by EmailReplyParser. The solution I found that should work for any HTML-formatted email is to remove all `<table>` and `<blockquote>` tags. Actual `<table>` elements (to be interpreted by markdown) should already be encoded with e.g. `&lt;table&gt;` - the only failure mode is if there is an *actual* HTML table in the content itself, which we wouldn't be able to support easily anyways.

The gem `html2text` traverses the HTML tree and outputs text - and markdown in the case of HTML links or images.

See merge request !7397

Improve consistency of empty todo list messages

- They all now end with punctuation
- Not everyone enjoys, or can even drink, coffee
- The "High five!" message had no context for why we were high-fiving
- "Henceforth" is one word

[ci skip]

See merge request !7572

Precalculate authorized projects in database

## What does this MR do?
It caches user's authorized projects in database instead of using multiple unions, which should simplify and speed-up things since this operation (getting authorized projects) is used a lot.

## Are there points in the code the reviewer needs to double check?
Did we miss a scenario where we need to refresh the list of projects?

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [ ] ~~API support added~~
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
#23150 

See merge request !6839

Less intrusive system note

## What does this MR do?
This MR is for making system notes less intrusive by implementing proposed design
 
## Are there points in the code the reviewer needs to double check?
System notes are reusing in issues, commits and MR discussions. May need to double check to make sure that the design is not breaking anywhere

## Why was this MR needed?
This merge request solve issue #19797 

## Screenshots (if relevant)
**Before:**
![merge-request-before](/uploads/91953598087a613078d80333a43815a7/merge-request-before.png)
**After**
![2016-11-15_17.41.46](/uploads/c809ba53cc34ee83bb439ed741dc39f3/2016-11-15_17.41.46.gif)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
#19797, #23129

See merge request !6755