Adds enum traits for argument factory and tests for those traits. Added
enum.
Adds add_judges action to arguments_controller.
Adds arguments/_add_judges partial
Removes submitted_to_judgement enum.  Adds argument#has_judges? and argument#eligible_judges.
Adds traits to argument factory for setting enum states.
Adds scope for selecting elegible judges.
Adds policy for arguments#add_judges
Adds policy guarded if for showing add_judge partial to arguments/show.
Adds route for arguments#add_judges
Adds con side invites feature tests and supporting model tests.