Update "Installation from source" guide for 8.15.0

Following the steps from https://gitlab.com/gitlab-org/release-tools/blob/master/doc/release-candidates.md#creating-rc1.

See merge request !8015

Resolve "Provide SVG as a prop instead of hiding and copy them in environments table"

## What does this MR do?
- Provides SVG as a prop instead of manually manipulate the DOM to show it 
- Uniforms all props names in environments related components, 3 formats were being used and it was error prone
- Adds tests for the new SVG props.

## Why was this MR needed?
Technical debt.

## 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
  - [x] 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?
Closes #25374

See merge request !7992

Displays milestone remaining days only when it's present

See merge request !7998

Do not reload diff for merge request made from fork when target branch in fork is updated

Closes #25263

See merge request !7973

API: Ability to remove source branch

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23577

See merge request !7804

Fix comments tab disappearing

Fixes #25272

See merge request !7913

Render SVG images in notes

Closes #24937 

See merge request !7747

Update JIRA troubleshoot documentation

closes #25152

See merge request !7977

Improvements to setting up SSH documentation

## What does this MR do?

Improves the documentation article on setting up SSH. 

* Added introduction
* Added additional explanations
* Added sub headings
* Moved sections around
* Added section about generating an SSH key pair on Windows with PuttyGen (will be expanded further in future)

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/24708

See merge request !6571

[ci skip]

The target branch of a merge request has to be a branch in the project
for which the merge request is submitted. When a branch changes in a fork,
it does not make sense to reload diffs of merge requests in the upstream
project that use the same branch name as the target branch.
Please note that it does make sense to reload diffs when the source branch
changes.

Update docs to reflect new defaults on omnibus

## What does this MR do?

Updates docs, after gitlab-org/omnibus-gitlab!1154 the flow has changed.

See merge request !8006

[ci skip]
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix active nav badges not inheriting the link color

## What does this MR do?

Fix active navigation and tabs badges not inheriting the link color (in this case, black).

## Screenshots (if relevant)

![image](/uploads/ab4e8ea99531106f9ddc4297e10c327b/image.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)

See merge request !7950

Fixed Wrong Tab Selected When Loggin Fails And Multiple Login Tabs Exists

## What does this MR do?
Fixes issue: 15081 Wrong Tab Selected When Loggin Fails And Multiple Login Tabs Exists
This is done by saving into a cookie when the active tab changes and by always selecting that tab when the page is loaded.
## Are there points in the code the reviewer needs to double check?
No
## Why was this MR needed?
In order to fix the issue: 15081
## Screenshots (if relevant)

## 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
  - [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?


Closes #15081

See merge request !7314

For mattermost chat commands, new defaults are set in the next release
making configuring easier. This commit reflects that in the doc.

[ci skip]

Updating reference to database password

## What does this MR do?

Updates references to postgresql['sql_password'] to use gitlab_rails['db_password'] instead. Original value is not used anywhere. For gitlab-org/omnibus-gitlab#1392 we're using gitlab_rails['db_password'] to create a .pgpass as needed.

See merge request !8000

Add nested groups support on data level

## What does this MR do?

- [x] Add  `parent_id` field to `Namespace`model. 
- [x] Create new database table `routes` that keeps information about full path to each group or project
- [x] Remove uniq index from `namespaces.path`
- [x] Add uniq index on `routes.path`
- [x] Fill routes table with path data from namespaces and projects
- [x] Change Namespace/Project URL lookup by routes table
- [x] Rename related routes (nested groups, projects) when parent path changes

This is solely backend preparation. UI, Permissions and API support will be added in separate merge request.   
 
## Are there points in the code the reviewer needs to double check?

migrations, Route model, Routable concern

Will require downtime. See https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7121#note_19490281 discussion

## Why was this MR needed?

One step further to full nested groups support

## Screenshots (if relevant)

No UI changes in this merge request so far

## 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
  - [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?

https://gitlab.com/gitlab-org/gitlab-ce/issues/2772

See merge request !7121

Replace MR access checks with use of MergeRequestsFinder

Split from !2024 to partially solve https://gitlab.com/gitlab-org/gitlab-ce/issues/23867

⚠ - Potentially untested
💣 - No test coverage
🚥 - Test coverage of some sort exists (a test failed when error raised)
🚦 - Test coverage of return value (a test failed when nil used)
✅ - Permissions check tested

- [x] 💣  app/finders/notes_finder.rb:17
- [x] ⚠  app/views/layouts/nav/_project.html.haml:80 [`.count`]
- [x] 💣  app/controllers/concerns/creates_commit.rb:84
- [x] 🚥  app/controllers/projects/commits_controller.rb:24
- [x] 🚥  app/controllers/projects/compare_controller.rb:56
- [x] 🚦  app/controllers/projects/discussions_controller.rb:29
- [x] ✅  app/controllers/projects/todos_controller.rb:27
- [x] 🚦  app/models/commit.rb:268
- [x] ✅ lib/gitlab/search_results.rb:71

- [x] https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2024/diffs#d1c10892daedb4d4dd3d4b12b6d071091eea83df_267_266 Memoize ` merged_merge_request(current_user)`
- [x] https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2024/diffs#d1c10892daedb4d4dd3d4b12b6d071091eea83df_248_247 Expected side effect for `merged_merge_request!`, consider `skip_authorization: true`.
- [x] https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2024/diffs#d1c10892daedb4d4dd3d4b12b6d071091eea83df_269_269 Scary use  of unchecked `merged_merge_request?`

See merge request !2033

Don't accidentally mark unsafe diff lines as HTML safe

Fixes potential XSS issue when a legacy diff note is created on a merge
request whose diff contained HTML

See https://gitlab.com/gitlab-org/gitlab-ce/issues/25249

See merge request !2040

Add authentication_token to filter_parameters list

See merge request !2041

Destroy a user session when they delete their own account via browser

This patch destroys a user's session when they delete their own account
using a browser. A new session is created as they are redirected to the
sign_in page.

Issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/25015

See merge request !2042

fix features_visibility_spec.rb

remove strange part of spec

fix conditions of comments tab disappearing and fix spec

generate changelog

rewrite spec for more coplex check step-by-step

move conditional logic into helper and fix changelog

fix indentation in helper

Fix JS error when reseting new issue template

Fixes JS error when trying to reset template when no template has been set.

See merge request !7978

postgresql['sql_password'] is not used, should be
gitlab_rails['db_password']

Fade out should be white instead of gray

Currently, you can see the hard edge of the fade out because it's a light shade of gray rather than white.   
Before:   
![Screen_Shot_2016-12-07_at_12.36.10_PM](/uploads/c8fd2c6ba1742d1260614fd4c9cb29c9/Screen_Shot_2016-12-07_at_12.36.10_PM.png)
After:   
![Screen_Shot_2016-12-07_at_12.35.53_PM](/uploads/52b51e4a825658a0c440e0f1fb86a31c/Screen_Shot_2016-12-07_at_12.35.53_PM.png)
cc @nmrony

See merge request !7979

Various small emoji positioning adjustments

## What does this MR do?
It changes various emoticon related css rules with very small minor tweaks of 1 or 2 px

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

## Why was this MR needed?
aesthetics

## Screenshots (if relevant)
-


## 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)
- [ ] 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?
none

See merge request !7993

Fixed timeago re-rendering every element

## What does this MR do?

Fixes an issue when new notes are added timeago will be initialised for every timeago element on the page again and therefore adding more timeouts.

See merge request !7969