Cache rendered Markdown fields in the database

## What does this MR do?

Introduces cache fields for Markdown-containing fields in the database, and populates them.

## Why was this MR needed?

Rendering Markdown into HTML is performance-intensive. A Redis cache already exists, but this approach is expected to be more performant and reduce unnecessary cache invalidations.

## What are the relevant issue numbers?

Closes #18337

See merge request !6095

Add notice about HTTPS cloning for CI

## What does this MR do?
Adds a notice about potential problem with GitLab CI unable to clone sources: https://gitlab.com/gitlab-org/gitlab-ce/issues/22484#note_16612187

## Issues
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/22484

See merge request !6719

Add tooltip to project fork count

## What does this MR do?

Adds a tooltip reading `Forks` when a user hovers over the count of project forks.

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

## Why was this MR needed?

Requested in #23066 

## Screenshots (if relevant)

![image](/uploads/023af8dc4df68549705f6a328cf8031c/image.png)

## 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
  - [ ] 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 you do - 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?

#23066

See merge request !6718

This commit alters views for the following models to use the markdown cache if
present:

* AbuseReport
* Appearance
* ApplicationSetting
* BroadcastMessage
* Group
* Issue
* Label
* MergeRequest
* Milestone
* Project

At the same time, calls to `escape_once` have been moved into the `single_line`
Banzai pipeline, so they can't be missed out by accident and the work is done
at save, rather than render, time.

Truncato is introduced as a dependency to intelligently shorten the rendered
HTML to 200 characters; the previous approach could have resulted in invalid
HTML being rendered.

This commit adds a number of _html columns and, with the exception of Note,
starts updating them whenever the content of their partner fields changes.

Note has a collision with the note_html attr_accessor; that will be fixed later

A background worker for clearing these cache columns is also introduced - use
`rake cache:clear` to set it off. You can clear the database or Redis caches
separately by running `rake cache:clear:db` or `rake cache:clear:redis`,
respectively.

Memoize ActiveRecord::Migrator.migrations in tests

See merge request !6723

Change issue board defaults

#### What does this MR do?
Changes the issue board default list from `Development`, `Testing`, `Production`, `Ready` to `To Do` and `Doing`

#### Screenshots (if relevant)
![Screen_Shot_2016-10-06_at_8.46.48_AM](/uploads/6e73e03f5749f18b95bd7e23c676603d/Screen_Shot_2016-10-06_at_8.46.48_AM.png)
![Screen_Shot_2016-10-06_at_9.07.06_AM](/uploads/cadd3af74e3adb73fe854478ce95120e/Screen_Shot_2016-10-06_at_9.07.06_AM.png)

#### What are the relevant issue numbers?
Closes #23025

See merge request !6716

Fix inconsistent highlighting of already selected activity nav-links

## What does this MR do?

*  Remove edge case where user could deselect an activity nav-link (which seems to be returning all the events)
*  Explicitly add an `All` tab to return all the events

## Are there points in the code the reviewer needs to double check?
Shouldn't be

## Why was this MR needed?
Resolves existing UI inconsistency

## Screenshots (if relevant)
Before:
![4OzkoQVJYc](/uploads/fd2a7fdbde2159e875482ec7b828fe60/4OzkoQVJYc.gif)

After:
![E0lj8UhEUU](/uploads/7eb5155861eb79d72957de04c9f172c9/E0lj8UhEUU.gif)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [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 you do - 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 #21631
*  Closes #21452


See merge request !6091

Use gitlab-workhorse 0.8.4

Fixes Go 1.5 compatibility broken in 0.8.3.

See merge request !6712

Link to Registry docs from project settings

Add an icon with a link to the docs from the project settings.

See merge request !6726

Update profile view

## What does this MR do?
Centers entire profile information section

## Screenshots (if relevant)
Before:
![Screen_Shot_2016-10-03_at_4.23.03_PM](/uploads/bc2017e88cb52ec0e817c4c59e70a186/Screen_Shot_2016-10-03_at_4.23.03_PM.png)

After:
![Screen_Shot_2016-10-03_at_4.21.57_PM](/uploads/86ce1339d21cc39a64c22f27868a2986/Screen_Shot_2016-10-03_at_4.21.57_PM.png)

## Does this MR meet the acceptance criteria?

- [ ] [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
  - [ ] 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 you do - 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 https://gitlab.com/gitlab-org/gitlab-ce/issues/22829

cc @dzaporozhets

See merge request !6662

Move user#show and group#show routing under root url

## What does this MR do?

Changes routing so user#show and group#show routing is under root url 

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

no

## Why was this MR needed?

For nice and consistent routing  for user/group show pages:

| before | after| 
|---|---|
| `/u/dzaporozhets` | `/dzaporozhets`| 
| `/dzaporozhets/gitlab-ce` |`/dzaporozhets/gitlab-ce`| 
| `/u/dzaporozhets/snippets` |`/u/dzaporozhets/snippets`| 
| `/groups/gitlab-org`|  `/gitlab-org`| 
| `/gitlab-org/gitlab-ce`|  `/gitlab-org/gitlab-ce`| 
| `/groups/gitlab-org/issues `|  `/groups/gitlab-org/issues `| 

So show page for user and group shown as `/:name` which is much nicer than before. At same time all nested pages like group issues stays under REST `/groups/:name/issues` so we don't need to introduce extra name restrictions ( ex. case when group has project with name "issues")

## Screenshots (if relevant)

## 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 you do - 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 https://gitlab.com/gitlab-org/gitlab-ce/issues/3620

See merge request !6686

Improve issue load time performance by avoiding ORDER BY in find_by call

See merge request !6724

Move container_registry user docs to new location

## What does this MR do?

Move container_registry user docs to new location and refactor them a bit.

Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/3349

## Moving docs to a new location?

See the guidelines: http://docs.gitlab.com/ce/development/doc_styleguide.html#changing-document-location

- [ ] Make sure the old link is not removed and has its contents replaced with a link to the new location.
- [ ] Make sure internal links pointing to the document in question are not broken.
- [ ] Search and replace any links referring to old docs in GitLab Rails app, specifically under the `app/views/` directory.
- [ ] If working on CE, submit an MR to EE with the changes as well.

See merge request !6516

Replace bootstrap caret with fontawesome caret

## What does this MR do?

1. Replaces all occurrences of `.caret` with fontawesome's caret (`fa-caret-down` for most cases)
2. Remove `.caret` from CSS
3. Refactored pipeline graph toggle to display the correct fontawesome caret (Had to change some JavaScript for this)  

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

*  Need to check if I missed any pages 😥 or for any side effects

## Why was this MR needed?
Resolves UI inconsistency

## Screenshots (if relevant)
Before (1 example out of many):
![Screen_Shot_2016-09-12_at_3.49.58_PM](/uploads/5eb93bbcc00412a5875e39302f4d8ba0/Screen_Shot_2016-09-12_at_3.49.58_PM.png)

After:
![Screen_Shot_2016-09-12_at_3.49.48_PM](/uploads/9259a9ebfb0bd09b4cfd55674e9b8be4/Screen_Shot_2016-09-12_at_3.49.48_PM.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [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 you do - 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 #21169

See merge request !6314

The Sortable concern has a default scope that adds ORDER BY to all
queries. EXPLAIN ANALYZE shows that this additional ORDER BY statement
causes the SQL optimizer to use the wrong index, which leads to a load
time of 2.9 s vs 0.073 ms just for the SELECT call. The minimal
change here is to re-implement find_by using where and reorder to
remove the ORDER BY clause in IssuesController#index.

Closes #23075

Only hide deploy status external link on x-small screens.

## What does this MR do?

Fixes [a regression](https://gitlab.com/gitlab-org/gitlab-ce/commit/03ea01946524a74773b24430c81804c2724b84b6#68dead621eaa630b5150a4d71b59fa3cd19030fd_57_50) where the deploy status widget hides only the text within the widget, and only for screens within bootstrap's 'small' range (≥544px - <768px).
 
## Are there points in the code the reviewer needs to double check?

I changed the viewport width range to hide the widget from `sm` to `xs` because when the external link is removed, it seems to fit comfortably even on xs viewports. 

Given that we were already hiding the external link (along with all of the deploy text) on `sm` viewports, I assume it's okay to hide the external link still, instead of wrapping it to a new line. 

We could remove the conditional hiding altogether though, and allow the external link to wrap. Definitely doesn't look as nice, but if it's important to show the external link along with the deploy status, we could make it look better when it wraps.

## Why was this MR needed?

Looked buggy, and prevented context being given for build passed icon on smaller screens.

## Screenshots (if relevant)

Before: 

![57efae92cd57c192075546](/uploads/22b278756de4ca6ab3949a4a9692994e/57efae92cd57c192075546.gif)

After: 

![57efaeb41b211194979047](/uploads/b178ddfbbdcfe74d2ce9f52e989a6878/57efaeb41b211194979047.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)
- [x] API support added
- Tests
  - [ ] 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 you do - 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/22778

cc: @jschatz1

See merge request !6633

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

[ci skip]

Closes https://gitlab.com/gitlab-org/omnibus-gitlab/issues/1433

See !6543.

Signed-off-by: Rémy Coutable <remy@rymai.me>

Added CC0 license to list of licenses

Adds a "license" (actually a deed, because its a dedication to the public domain) to the appropriate place in the documentation.

It adds another relevant license to our documentation.

See merge request !6622