Move persistent warnings from ApplicationController to a concern
Decrease importance of persistent warnings on controllers

Notices set in another actions should overwrite the persistent ones.
Hide persistent warnings when contributing
Merge branch 'master' into im-remove-duplicated-flash-msgs
Merge branch 'master' into im-hide-persistent-warnings-when-contributing

Conflicts:
	app/controllers/concerns/persistent_warnings.rb
	spec/controllers/concerns/persistent_warnings_spec.rb