Merge CE 7.3.0.rc1

See merge request !178

Conflicts:
	Gemfile.lock
	VERSION
	doc/README.md
	doc/install/installation.md

Document the extra.sign_in_text setting for CE

See merge request !1027

Check for hooks directory symlink in gitlab:check

See merge request !1094

Dont rebase pushed commits

/cc @jacobvosmaer

See merge request !1095

Add dormant New Relic gem

See merge request !1089

The gem can be enabled and configured via environment variables.

Merge 7.3.pre CE to EE

See merge request !177

Merge 79190fe0 (7.3.0-pre) and serialize_service_properties

This combines two merges because each individual merge breaks the build on its own.

See merge request !175

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

API MR ordering

Fixes #1477

See merge request !1076

Use sockets to connect to Redis

See merge request !1088

Fix LdapGroupLink error message

See merge request !176

Merge remote-tracking branch 'subscribers/serialize_service_properties' into merge-79190fe0-7.3.0-pre

ActiveModel::Validations has an 'errors' attribute, but no 'error'.

First I did `rake dev:setup` at 405a5acb; then `rake db:migrate` at
e93523ed.

Conflicts:
	Gemfile
	README.md
	VERSION
	db/schema.rb
	doc/install/installation.md
	lib/gitlab/git_access.rb
	lib/gitlab/ldap/user.rb
	spec/lib/gitlab/ldap/access_spec.rb

Implement comments on parallel diff

Fixes #1565

See merge request !1090

Feature oauth refactoring

See merge request !173

Fix grammatical error in 'not merged changes' msg

Update user_management.md

Adding ability to configure webhook timeout via gitlab.yml