Port Permission Group Admin to Angular
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Migrate the Admin => Server Admin => Permission Groups admin page to 
Angular.

As an added feature, the interface now displays inherited permissions
alongside linked permissions for each group.  Inherited permissions
are read-only and act to indicate to the user when a group already has
a certain permission and therefore may not need a new one added.

Additionally, a new filter option is available in the linked permissions
interface for filtering the displayed linked permissions by code or 
description.