Refactor description templates documentation

## What are the relevant issue numbers?

Refactors docs introduced by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4981

See merge request !5839

Add pipeline graph

## What does this MR do?
Adds pipeline visualization

## What are the relevant issue numbers?
Closes #18141    
Part of #19982 

## Screenshots (if relevant)
![Screen_Shot_2016-08-16_at_7.59.52_PM](/uploads/c9dd695d2ddbd2a85e98a5b4e500d52c/Screen_Shot_2016-08-16_at_7.59.52_PM.png)
![Screen_Shot_2016-08-16_at_7.55.49_PM](/uploads/5ab548cc5fc8a42371d3b54108798c02/Screen_Shot_2016-08-16_at_7.55.49_PM.png)

See merge request !5742

Collapse build tabs that don't fit

## What does this MR do?
* Orders tests from `failed` > `pending` > `running` > `canceled` > `skipped` > `success`
* Put stages in one dropdown
* Once stage is selected, second dropdown shows all builds/jobs for that stage

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

## Why was this MR needed?
So many tests!   
<img src="/uploads/d581b2670588121c6d64823f61906a1a/Screen_Shot_2016-08-01_at_9.52.50_AM.png" width="600px">

## What are the relevant issue numbers?
Closes #18516    
Part of #19982

## Screenshots (if relevant)
![Screen_Shot_2016-08-17_at_1.14.20_PM](/uploads/fa183361ed13137257caf20a6afc4ef1/Screen_Shot_2016-08-17_at_1.14.20_PM.png)
![Screen_Shot_2016-08-17_at_1.14.39_PM](/uploads/f568cac463abf5c625cf31912ddbd00a/Screen_Shot_2016-08-17_at_1.14.39_PM.png)

See merge request !5595

Fix icon alignment of star and fork buttons

## What does this MR do?

Fix alignment of star and fork icons.

## Why was this MR needed?

Buttons had more padding on the left than on the right.

## What are the relevant issue numbers?

fixes #20001 

## Screenshots

<table>
<thead><th>Before</th><th>After</th></thead>
<tr>
  <td><img alt="fork-button-before" src="/uploads/664c0bc935f4c48899f5b63a1c215cbc/fork-button-before.png"></td>
  <td><img alt="fork-button-after" src="/uploads/9385427a5b178487bd24cd2f8ec4a5ed/fork.png"></td>
</tr>
<tr>
  <td><img alt="project-buttons-before" src="/uploads/48ef41458433b468afc2919eb24849cc/project-buttons-before.png"></td>
  <td><img alt="project-buttons-after" src="/uploads/3bafe6e68645d787a2cdb79cd164335f/project-actions.png"></td>
</tr>
</table>

See merge request !5451

Remove sleep calls introduced in !5740

See merge request !5815

Send notification emails when users are newly mentioned in issue or MR edits

## What does this MR do?

Introduces "new mention in issue" and "new mention in MR" email notifications.  Editing a Mentionable title or description and adding a mention to a user who was not previously mentioned will now send them a notification email, following usual permissions for doing so.

## Why was this MR needed?

Issues & MRs may be edited to include mentions to new people. We don't currently send out email notifications of these edits to anyone, although they do create TODOs. This brings email notifications into parity with TODOs.

## What are the relevant issue numbers?

Closes #2451

See merge request !5800

Hide "Create new list button" on Issues and MRs pages

![1](/uploads/d8b08cb62cfc9e9d29e3e64b2ed0a8af/1.png)

/cc @jschatz1 

See merge request !5852

Add delimiter to project stars and forks count

## What does this MR do?
Adds the `number_with_delimiter()`to the project stars and fork counts on the projects dashboard.

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

## Why was this MR needed?
Improve readability and adhere to the [UI guide](https://gitlab.com/help/development/ui_guide.md#counts)

## What are the relevant issue numbers?
Closes #20746 

## Screenshots (if relevant)
Before:
![Screen_Shot_2016-08-09_at_1.30.44_PM](/uploads/69592ce220d64774e265cfbcfcb6864a/Screen_Shot_2016-08-09_at_1.30.44_PM.png)

After:
![Screen_Shot_2016-08-09_at_1.30.58_PM](/uploads/1470179256614c2e47cc9d0e49aeaf09/Screen_Shot_2016-08-09_at_1.30.58_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 [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)

See merge request !5741

Fix merge request new view not changing code view rendering style

Correctly respects the code view changing when creating a merge request.

Closes #20808

See merge request !5768

Issue boards

## What are the relevant issue numbers?

- Issue: #17907 
- Issue backend: #20335 
- Backend MR: !5548
- Frontend MR: !5554
- Documentation !5713 

## Screenshots (if relevant)

## 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
  - [x] Added for this feature/bug
  - [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)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5548

Fix diff comments inverted toggle bug

## What does this MR do?
Explicitly set the comments visibility toggle based on the `active` css class.

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

## Why was this MR needed?
Fixes existing UI bug

## What are the relevant issue numbers?
Closes #20898 

## Screenshots (if relevant)
Before:
![A1ccIDEWsI](/uploads/21175e2008ee4e00225c22afebd873aa/A1ccIDEWsI.gif)

After:
![jHoFp69mAK](/uploads/e85f429d60a4e56d588faec51cd8648a/jHoFp69mAK.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)

See merge request !5818

Tracking of custom events

## What does this MR do?

This MR adds the ability to track custom events such as the number of Git pushes.

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

The usual stuff.

## Why was this MR needed?

We want to track more business level data such as the number of Git pushes, how many repositories are imported (and from where), etc.

## What are the relevant issue numbers?

gitlab-org/gitlab-ce#13720

## 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
  - [x] Added for this feature/bug
  - [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)

cc @pcarranza 

See merge request !5830

Issue boards UI

## What does this MR do?

UI for issue boards.

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

## Why was this MR needed?

## What are the relevant issue numbers?

-  Issue: #17907
-  Backend MR: !5548
-  Frontend MR: !5554
- Documentation !5713 

## Screenshots (if relevant)

![Screen_Shot_2016-08-17_at_14.06.06](/uploads/e2abed987d2c2d280e8b8034c8949024/Screen_Shot_2016-08-17_at_14.06.06.png)


See merge request !5554

# Conflicts:
#	app/controllers/projects/merge_requests_controller.rb

Resolve "Pipelines for merge request"

## What does this MR do?
Adds `Pipelines` tab in merge request view

## What are the relevant issue numbers?
Closes #18681 

## Screenshots (if relevant)
![Screen_Shot_2016-08-16_at_3.22.41_PM](/uploads/c04febab3765b1fac2bf3bbfb9882f9f/Screen_Shot_2016-08-16_at_3.22.41_PM.png)

See merge request !5485

Eliminate unneeded calls to Repository#blob_at when listing commits with no path

See merge request !5848

It wasnt testing what it was saying it should be...