Update Role, renaming 'name'->'label' for consistancy with other models

Also removed the unused 'description' field.
Rename 'roles' to 'groups' in User model

Also update APIv2 with corresponding changes.
Add '/groups' endpoint to APIv2
Remove unused field from User model
Merge branch 'apiv2_updates'

* apiv2_updates:
  Remove unused field from User model
  Add '/groups' endpoint to APIv2
  Rename 'roles' to 'groups' in User model
  Update Role, renaming 'name'->'label' for consistancy with other models