Sub navigation

## What does this MR do?
Styles sub nav   
cc @dzaporozhets  @skyruler @jschatz1 

## What are the relevant issue numbers?
#18058 and #17983 

## Screenshots (if relevant)
![Screen_Shot_2016-06-03_at_12.10.26_PM](/uploads/8b948c32699a93ab0a390bda31e0e411/Screen_Shot_2016-06-03_at_12.10.26_PM.png)
![Screen_Shot_2016-06-03_at_12.10.34_PM](/uploads/241115c35d0618f3de739be9a670416d/Screen_Shot_2016-06-03_at_12.10.34_PM.png)

See merge request !4468

Implement compact side nav

## What does this MR do?
Implements new compact nav design   
Note- new navbar icons are in a separate MR (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4268)

## What are the relevant issue numbers?
Closes #18013 

## Screenshots (if relevant)
![Screen_Shot_2016-06-02_at_3.20.37_PM](/uploads/d31bd17ae47743f1a20d7429b4396e84/Screen_Shot_2016-06-02_at_3.20.37_PM.png)   
![Screen_Shot_2016-06-02_at_3.20.43_PM](/uploads/d03a080a57707b6a2161127f3904fcd5/Screen_Shot_2016-06-02_at_3.20.43_PM.png)

cc @dzaporozhets 

See merge request !4447

Instrument `RepositoryCheck::SingleRepositoryWorker` manually

See merge request !4446

This worker is called manually by `RepositoryCheck::BatchWorker` meaning it's not tracked automatically by the Sidekiq middleware.

Add new GitLab CI configuration facade class

## What does this MR do?

This MR is a first iteration of major CI configuration refactoring. See #17139 and #15060 for more details.

## What are the relevant issue numbers?

Closes #17139

See merge request !4462

Ability to prioritize labels

Closes #14189 

See merge request !4009

Fix knapsack for master

It were mistakenly to invoke `rspec` where it should invoke `spinach`.


See merge request !4510

Use Knapsack to evenly distribute specs

Try to distribute all tests evenly accross all nodes to reduce the testing time of GitLab CE.

This uses high amount of auto-scaled machines.


See merge request !4240

Added 8.9 install/update guides

See merge request !4507

[ci skip]

Workhorse to serve raw diffs

Fixes (partially) #13999

Dependent on: gitlab-org/gitlab-workhorse!45

See merge request !4130

Rename ci_commit in application code

This is third iteration of renaming `[ci_]commit(s)` in application code to `pipeline(s)`.


See merge request !4464

Rename Ci::Commit in specs

This is second iteration of renaming Ci::Commit occurences, this time I try to rename all `let's` and `factories` to match what type of object is created:

1. Rename factories: `ci_[...]_commit_[...]` to `ci_[...]_pipeline_[...]`,
2. Rename all `let's(:[ci_]commit)` to `let(:pipeline)`,
3. Rename all occurrences of `[ci_]commit` to `pipeline` if Pipeline object is created

cc @grzesiek @DouweM 

See merge request !4463