DDF-669 DDF-670 DDF-682

DDF-670 - Restyles the admin application modules.  Setup initial application selection page for Jeren and Sam's work.

DDF-669 - Created Feature management backend API and Feature UI via
config plugin.

DDF-682 Created configuration plugin API framework.  Adjusted
configuration UI to work within a Configuration Plugin.
I rembember not wanting to muck with this class too much when doing the restyling.  We could handle it in the template if we converted this to a Marionette.CompositeView (aka CollectionView with a template).