Enables frozen string for the following:

* app/controllers/*.rb
* app/controllers/admin/**/*.rb
* app/controllers/boards/**/*.rb
* app/controllers/ci/**/*.rb
* app/controllers/concerns/**/*.rb

Partially addresses #47424.

CE upstream - 2018-09-18 21:21 UTC

Closes gitlab-org/release/framework#15

See merge request gitlab-org/gitlab-ee!7408

# Conflicts:
#	app/models/concerns/protected_ref_access.rb
#	app/models/epic.rb

[ci skip]

Remove EE-specific lines from Plan concerns

See merge request gitlab-org/gitlab-ce!21448

Remove EE-specific lines from Plan concerns

Closes #6122

See merge request gitlab-org/gitlab-ee!7202

Enhance some performance guideline titles

See merge request gitlab-org/gitlab-ce!21797

[QA] consolidate selector patterns (1_manage/login)

See merge request gitlab-org/gitlab-ce!21711

Use a JWT header to synchronize the default branch

Closes #7619

See merge request gitlab-org/gitlab-ee!7405

Improve Emoji detection in commit messages

Closes gitlab-org/release/framework#15

See merge request gitlab-org/gitlab-ce!21799

CE upstream - 2018-09-18 18:21 UTC

See merge request gitlab-org/gitlab-ee!7406

Resolve "Enable Auto DevOps by default for self managed instances of GitLab"

Closes #41729

See merge request gitlab-org/gitlab-ce!21157

# Conflicts:
#	locale/gitlab.pot

[ci skip]

Improve cluster apps installation flow

Closes #50111

See merge request gitlab-org/gitlab-ce!21567

Improve TabHelper to clarify the use of Namespaces for the nav_link

See merge request gitlab-org/gitlab-ce!21787

Docs: fix typo

See merge request gitlab-org/gitlab-ee!7404

Don't use MilestoneFinder for group milestones

Closes #51546

See merge request gitlab-org/gitlab-ce!21780

Update alert docs for support for library metrics

See merge request gitlab-org/gitlab-ee!7380

CE upstream - 2018-09-18 12:21 UTC

See merge request gitlab-org/gitlab-ee!7401

Document the use of and need for using feature flags more frequently

See merge request gitlab-org/gitlab-ce!21478

This adds a development guide explaining that we are going to use
feature flags more often, why, what the benefits are, and so on.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/49619 for more
information.

46733 move filter dropdown from font awesome to our own icons ee

Closes gitlab-ce#46733

See merge request gitlab-org/gitlab-ee!7356

Resolve "Move filter dropdown from Font Awesome to our own icons"

Closes #46733

See merge request gitlab-org/gitlab-ce!21694

This refactors the DashboardGroupMilestone model so that it no
longer uses the MilestoneFinder, instead using methods defined
on the Milestone model directly.

This changes our Danger integration so that it is smarter about
detecting GitLab emoji in commit messages. This is done using a two step
process:

1. We use the old regular expression to determine if a commit message
   _might_ include an emoji.

2. If this regular expression matches, we then check for all existing
   emoji names in the commit message. This might be a wee bit expensive,
   but because we couple it with the previous step it should be rarely
   executed.

This ensures we don't trigger an error when a commit message includes
text such as `:foo:bar:`, which is not a valid Emoji.

Fixes https://gitlab.com/gitlab-org/release/framework/issues/15

This enhances a few performance guideline titles in the development
README, making it easier to understand what topics they cover.

# Conflicts:
#	doc/install/requirements.md
#	spec/views/help/index.html.haml_spec.rb

[ci skip]