Parse Repository URLs with Addressable instead of URI

Addressable is more modern than URI and supports scp-like URLs which are
common when referencing Git repositories.

REF: https://gitlab.com/gitlab-com/support-forum/issues/667
Sentry: https://sentry.gitlap.com/gitlab/gitlabcom/issues/4324

See merge request !397

Bump GitLab Pages to 0.2.4

This fixes 404 Content-Type that were supposed to be fixed last time.

cc @axil @dblessing 


See merge request !394

Sync 8-8-stable-ee to master

I solved some merge conflicts that arose when merging CE 8-8-stable (which contains the latest master branch) into 8-8-stable-ee.

See merge request !398

Tag API calls to /internal/authorized_keys

See merge request !396

CE upstream

See merge request !389

Addressable is more modern than URI and supports scp-like URLs which are
common when referencing Git repositories.

Fix minor typos in admin health check page

Fix minor typos from gitlab-org/gitlab-ce!3888

cc/ @DouweM @twk3 

See merge request !4134

Clean up EventsHelper spec

Extracted from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4090

See merge request !4133

Enable the Rubocop DeprecatedClassMethods cop

This reports uses of `File.exists?` and `Dir.exists?`, which were both
deprecated in Ruby and will eventually be removed in favor of `.exist?`.
Also fixes all existing uses of the deprecated methods.

See merge request !4087

Codestyle changes to make sure we have space around operators (EE)

This will introduce fixes for gitlab-org/gitlab-ce#17398 so after
gitlab-org/gitlab-ce!4112 gets merged and CE synced to EE, we don't
have failing builds.

See merge request !388

Fix a description for default scope on builds

Should be "**All* builds (from this project)" for the {project,admin}
builds page without scope.

Fix a regression on !2243 (#4240).

See merge request !4118

Add API endpoints for un/subscribing from/to a label



See merge request !4051

# Conflicts:
#	db/schema.rb

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

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

Closes #15638

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

These will fail until #558 is taken care of.