Engine: Activation Keys: several changes to support the Activation Keys UI

This PR contains the changes needed to perform basic CRUD actions on activation keys in the UI.  It also includes some 'common' changes that will be needed for other pages (e.g. fix pathing to several common assets).

At this point, was able to do testing of basic CRUD; however, once we have support for products/repos, manifest import, systems and system groups, we'll need to revisit to make sure those functions work in the Activation Keys UI.