Merge pull request #8020 from mr-vinn/note-trunc-link

Improve event note display in dashboard and project activity views
Add refactoring for multiple LDAP server support

These changes are ported from EE to CE. Apply changes for app directory
Add config changes for mutliple LDAP support (EE only)
Apply configuration changes for Multiple LDAP servers
Merge remote-tracking branch 'origin/master' into feature-multiple-ldap-servers

Conflicts:
	app/controllers/omniauth_callbacks_controller.rb
Refactor lib files for multiple LDAP groups
Merge tests to support Multiple LDAP groups
Remove unused method
DRY find method to find Gitlab user
Move dynamic omniauth declarations to initializer
Add specs for authentication and config
Fix authorization for LDAP login
Make sure the filters are applied
Use server specific uid
Add explaining note to authentication method [skip ci]
Add libravatar documentation.
Add a note about notification for a project.
Remove unused methods
Different wording for notification note.
Add a link to libravatar doc in gitlab.yml.example.