Also added the derective osPerms to check if the current user has permissions.
Removed old Django views and urls for user.
Created utils.views.APIView which should be used instead of the AjaxView.
Fixes: #1470Fixes: #1454
Refactored user creation and update via REST API. Used new serializer.
Cleaned up management commands, signals and imports. Moved code from 'api.py' to 'models.py'.
Changed usage of group 'Registered'. Now the users don't have to be members to gain its permissions. Used customized auth backend for this.
Added and changed some tests.
