Issuable sidebar tweaks

- Move cross-project reference down 
- ~~Fix "Notifications" label color~~ Reverted
- ~~Use regularly colored button for "Subscribe"/"Unsubscribe"~~ Reverted

Before:

![Screen_Shot_2015-12-15_at_17.38.08](/uploads/d4eeab44bb21fca2fe9ebe620ed9e060/Screen_Shot_2015-12-15_at_17.38.08.png)

After:

(Only the moved cross-project reference is still relevant, other changes have been reverted)

![Screen_Shot_2015-12-15_at_17.38.23](/uploads/b61aed3a0884c986785a5b09af8dbb25/Screen_Shot_2015-12-15_at_17.38.23.png)

cc @skyruler 

cc @rspeicher 8.3 please!

See merge request !2105

Fix double right border in MR discussion
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

# Before
![Screenshot_2015-12-16_15.44.00](/uploads/dd2c85e82fdb784e897cf1a695af1a1e/Screenshot_2015-12-16_15.44.00.png)

# After
![Screenshot_2015-12-16_15.43.36](/uploads/b50954e01bb3f45d2df6f43d34a1db60/Screenshot_2015-12-16_15.43.36.png)

cc @skyruler 

See merge request !2113

This reverts commit e4e1777a.

This reverts commit c1db8d15.

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

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

Revert "Make sure notify email always has author info."

This reverts commit 303f79f8.

See merge request !2103

Pass all requests from NGINX to gitlab-workhorse



See merge request !2073

Fix clipboard buttons on MR instructions and Commit#show



See merge request !2108

Add SVN to Git migration documentation

Document the process of migrating a SVN repository and pushing it to GitLab.

cc/ @axil

See merge request !2028

Fix time_ago_with_tooltip for activity feed

Closes #4002

See merge request !2074

Make profile navigation full wide
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

## Before


![Administrator___GitLab](/uploads/a43e8992264ed78afa732e7a911ef154/Administrator___GitLab.png)

## After

![Administrator___GitLab1](/uploads/9e67e8af071d4879045311abe15a7bba/Administrator___GitLab1.png)

See merge request !2076

[ci skip]

Move Markdown/reference logic from `Gitlab::Markdown` to `Banzai`

- Moves from `Gitlab::Markdown` to `Banzai`
- Moves filters and pipelines into their own namespace: `Banzai::Filter` and `Banzai::Pipeline`
- No more `autoload`!
- Split up `Gitlab::ReferenceExtractor` into `Banzai::ReferenceExtractor` and `Gitlab::ReferenceExtractor`
- Replace `something(load_lazy_references: true)` by `Gitlab::ReferenceExtractor.lazily { something }`

Goes from:

```ruby
def referenced_merge_requests
  references = [self, *notes].flat_map do |note|
    note.all_references(load_lazy_references: false).merge_requests
  end.uniq!

  Gitlab::Markdown::ReferenceFilter::LazyReference.load(references).uniq.sort_by(&:iid)
end
```

to

```ruby
def referenced_merge_requests
  Gitlab::ReferenceExtractor.lazily do
    [self, *notes].flat_map do |note|
      note.all_references.merge_requests
    end
  end.sort_by(&:iid)
end
```

See merge request !2027

Add user repository integrity check rake task

Corrupt repositories and stuck lock files can cause weird issues in
GitLab. Often we know which user is having these problems and then we
have to go hunt down which repository is causing it. Several times
recently that involved me running queries in the rails console to get
an array of projects and then writing a quick Ruby script to loop
through and run `git fsck`. This last time I also had to check for the
existence of `config.lock` and ref lock files. 

This rake task will eliminate all of those steps and allow an admin to
simply specify a username.

I also added the lock file checks to the existing `gitlab:repo:check`
task which goes through all projects. 

See merge request !2080

Increase fixed layout width to 1280px
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

cc @creamzy 

See merge request !2075

Fix inline panel heading height

The `line-height` was added so that headings in the panels on the settings page had the same height as headings elsewhere, but the style applied everywhere :)

Before:

(Look at the "Unstarted Issues" heading)

![Screen_Shot_2015-12-15_at_17.39.46](/uploads/9dbea4c8b28e3c43bb5d4b5226d7a1ec/Screen_Shot_2015-12-15_at_17.39.46.png)

![Screen_Shot_2015-12-15_at_17.40.19](/uploads/97898418e9a66954c02e8a68b21c08b9/Screen_Shot_2015-12-15_at_17.40.19.png)

After:

![Screen_Shot_2015-12-15_at_17.40.45](/uploads/5748aba032889053dd778b39e96fa301/Screen_Shot_2015-12-15_at_17.40.45.png)

![Screen_Shot_2015-12-15_at_17.40.40](/uploads/20240cdc7a6d5665cd32556d1a0e6c1d/Screen_Shot_2015-12-15_at_17.40.40.png)

cc @skyruler 

cc @rspeicher 8.3 please!

See merge request !2106

This reverts commit 303f79f8.

Add feature specs for note polling

Ref. #4032, !2084

cc @rspeicher 

See merge request !2086