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.
Application plugins should only allow iframe locations.  We do not want to load external javascript for application configuration plugins.