DDF-917 - added support for custom attributes in the enhanced search ui.

-added support for the grouped content type configuration.
-if no group content types are present, it should function normally.
-Adjusted Standard UI config to handle strings and List<String>.  work around for KARAF-1701.
-added tests for the new methods in the Standard Search UI Managed
Service.
Merge pull request #35 from McLucas/feature/DDF-917

DDF-917 - added support for custom attributes in the enhanced search ui.