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

# 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

Added VueJS plugin

## What does this MR do?

Adds the VueJS & Vue resource plugin with environment detection. 

## What are the relevant issue numbers?

Closes #20738 

See merge request !5845

Fix downtime check formatting

## What does this MR do?

This MR adjusts the formatting of the migration downtime checker so messages are more readable.

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

Not specifically

## Why was this MR needed?

Formatting was somewhat hard to read and the online/offline indicators used the wrong colour.

## New Format

```
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20140407135544_fix_namespaces.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705054938_add_protected_branches_push_access.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705054952_add_protected_branches_merge_access.rb
[offline]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705055254_move_from_developers_can_merge_to_protected_branches_merge_access.rb:

We're creating a `merge_access_level` for each `protected_branch`. If a user creates a `protected_branch` while this
is running, we might be left with a `protected_branch` _without_ an associated `merge_access_level`. The `protected_branches`
table must not change while this is running, so downtime is required.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5081#note_13247410

[offline]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705055308_move_from_developers_can_push_to_protected_branches_push_access.rb:

We're creating a `push_access_level` for each `protected_branch`. If a user creates a `protected_branch` while this
is running, we might be left with a `protected_branch` _without_ an associated `push_access_level`. The `protected_branches`
table must not change while this is running, so downtime is required.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5081#note_13247410

[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705055809_remove_developers_can_push_from_protected_branches.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705055813_remove_developers_can_merge_from_protected_branches.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160716115711_add_queued_at_to_ci_builds.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160725083350_add_external_url_to_enviroments.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160727163552_create_user_agent_details.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160728081025_add_pipeline_events_to_web_hooks.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160728103734_add_pipeline_events_to_services.rb
[offline]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160729173930_remove_project_id_from_spam_logs.rb:

Removing a column that contains data that is not used anywhere.

[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160801163709_add_submitted_as_ham_to_spam_logs.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160802010328_remove_builds_enable_index_on_projects.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160805041956_add_deleted_at_to_namespaces.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160810102349_remove_ci_runner_trigram_indexes.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160810142633_remove_redundant_indexes.rb
```

## Does this MR meet the acceptance criteria?

- 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)

See merge request !5840

[ci skip]

This removes excessive whitespace from the messages (e.g. leading
whitespace) and ensures the message is more clearly visible.

These JS errors are only thrown in PhantomJS, and enough of the page is
rendered properly that this spec passes. We should remove this in
future.

The colours were incorrect: offline was green and online was red,
instead of the opposite.

GitLab Performance Monitoring is now able to track custom events not
directly related to application performance. These events include the
number of tags pushed, repositories created, builds registered, etc.

The use of these events is to get a better overview of how a GitLab
instance is used and how that may affect performance. For example, a
large number of Git pushes may have a negative impact on the underlying
storage engine.

Events are stored in the "events" measurement and are not prefixed with
"rails_" or "sidekiq_", this makes it easier to query events with the
same name triggered from different parts of the application. All events
being stored in the same measurement also makes it easier to downsample
data.

Currently the following events are tracked:

* Creating repositories
* Removing repositories
* Changing the default branch of a repository
* Pushing a new tag
* Removing an existing tag
* Pushing a commit (along with the branch being pushed to)
* Pushing a new branch
* Removing an existing branch
* Importing a repository (along with the URL we're importing)
* Forking a repository (along with the source/target path)
* CI builds registered (and when no build could be found)
* CI builds being updated
* Rails and Sidekiq exceptions

Fixes gitlab-org/gitlab-ce#13720

Move to project dropdown with infinite scroll for better performance

See merge request !5828

Use just SQL to check is a user can admin_issue on a project

Tradeoff

- we duplicate how we check admin_issue in a SQL relation in the Ability class

Fix error message for existing labels in right sidebar.

## What does this MR do?
Fixes flash notification in right sidebar, if we want to create an existing label.

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

## Why was this MR needed?
Because it was broken.

## What are the relevant issue numbers?
Fixes #20117 

## Screenshots (if relevant)

#### Before
![https://gitlab.com/gitlab-org/gitlab-ce/uploads/c1fa7e98d1a3f0daaf8197809bbb26d0/Screen_Shot_2016-07-22_at_11.33.35.png](https://gitlab.com/gitlab-org/gitlab-ce/uploads/c1fa7e98d1a3f0daaf8197809bbb26d0/Screen_Shot_2016-07-22_at_11.33.35.png)

#### After
![Screen_Shot_2016-07-28_at_13.38.03](/uploads/1dca73bf4c1b14c0044952a5032d9325/Screen_Shot_2016-07-28_at_13.38.03.png)
![Screen_Shot_2016-07-28_at_13.41.18](/uploads/9b814f7f03d0314050659e1ac6ace290/Screen_Shot_2016-07-28_at_13.41.18.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~~
  - [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 !5546

Don't show comment button in gutter of diffs on MR discussion tab

When browsing to an MR, switching to the Changes tab, and switching back to the Discussions tab, the gutter of the diffs on that page would show the comment button on-hover, while it shouldn't, since comments on new lines can only be created from the Changes tab.

![Screen_Shot_2016-07-25_at_22.01.11](/uploads/6b044e1a3ecb34ddaa0af432833473aa/Screen_Shot_2016-07-25_at_22.01.11.png)

`8-10-stable` counterpart at https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5493

See merge request !5492

Updated Akismet documentation

Updated Akismet documentation

See merge request !5821

[ci skip]

Add hover state to todos

## What does this MR do?

- Add a hover state to todos like for repository files.
- Fix button alignment in todos
- Add link to avatar in todos

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

The `border-collapse` part—is there any better way?

## Why was this MR needed?

Make hover states consistent.

## What are the relevant issue numbers?

fixes #19833 

## Screenshots

### Before

![before](/uploads/cd2e7b234bf08fac48aebb60cdfa26a9/before.png)

### After

![todos-list](/uploads/592457050cb3ff2c43dfcce78418c50b/todos-list.png)

![todos-list-last-hover](/uploads/532714333bc74d1656a5c767012b4cdd/todos-list-last-hover.png)

![todos-mobile](/uploads/d542b04ddebc9d4354d57151dd04c0d2/todos-mobile.png)

See merge request !5361

Changed project description width

## What does this MR do?

Changes the width of the project description to a max of `700px`

## What are the relevant issue numbers?

Closes #20020 

## Screenshots (if relevant)

![Screen_Shot_2016-07-21_at_12.51.59](/uploads/567f5b11553b45baa7fb07156e46b727/Screen_Shot_2016-07-21_at_12.51.59.png)

See merge request !5397

Fixed width on project visibility icon in project list

## What does this MR do?

Gives fixed width to the project visibility icons in the project list so that they all correctly line up with each other.

## What are the relevant issue numbers?

Closes #19583 

## Screenshots (if relevant)

![Screen_Shot_2016-07-07_at_12.49.58](/uploads/bffa097c5c0e0a1339bbd4d7ea15d84f/Screen_Shot_2016-07-07_at_12.49.58.png)

See merge request !5137

Implement pipeline hooks, extracted from !5525

Closes #20115

See merge request !5620

Highlight empty lines

## What does this MR do?

Rather than just highlight the text, file line highlighting now highlights the full line including empty lines

## What are the relevant issue numbers?

Closes #19484 

## Screenshots (if relevant)

![Screen_Shot_2016-07-05_at_13.52.31](/uploads/d3bddc918d731681465381e96c0aa2b0/Screen_Shot_2016-07-05_at_13.52.31.png)

See merge request !5092

Load issue templates from repository

part of #18656 


## 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)

See merge request !4981

Backport changes from gitlab-org/gitlab-ee!581

## What does this MR do?

Backports changes that were made in gitlab-org/gitlab-ee!581, to avoid potential merge conflicts in the future.

## What are the relevant issue numbers?

- Related to gitlab-org/gitlab-ee!581

## Does this MR meet the acceptance criteria?

## Tasks

- [ ]  !5824 Backport changes from EE!581 to CE
    - [x]  Implementation
        - [x]  ::ProtectedBranches::CreateService.new
        - [x]  Can't remove `load_protected_branches_gon_variables`
        - [x]  `has_many` with count enforced
        - [x]  Extract from access levels
        - [x]  project.protected_branches.create(params)
        - [x]  Improve "access_levels.first"
        - [x]  Fix tests
    - [x]  Fix build
    - [x]  Assign to Douwe
    - [ ]  Wait for review/merge

See merge request !5824