Various changes for client and REST API.

- Admin dashboard changes.
- login page fixes for links.
- Moved login, logout, and registration tests to users controller.
- Using 'col-md' instead of 'col-sm' in HTML files.
- Added test for 'GET /studies/dto/processing'.
- client services should not return a response, but the JSON data instead.
- Users on server side have a status field now.
- Added JsonController so that all controllers return similar JSON results.
- Fixed problem with using com.typesafe.plugin.use[BbwebPlugin].