CORE, RPC, GUI: added support for listing direct admins with attributes

CORE:
- Added method getDirectRichAdminsWithSpecificAttributes() to VosManager,
  GroupsManager and FacilitiesManager.
- Added supportive method getDirectRichAdmins to Bl layer of same managers.

RPC:
- Added method getDirectRichAdminsWithSpecificAttributes() to
  VosManager, GroupsManager & FacilitiesManager.
- Added RPC javadoc above other getAdmins() like methods.

GUI:
- Show only direct admins when listing users assigned as admins of entity.
- Modified texts on empty admins tables.