CORE: added methods for listing direct rich admins with specific attributes

 - Added method getDirectRichAdminsWithSpecificAttributes() to VosManager,
   GroupsManager and FacilitiesManager.
- Added supportive method getDirectRichAdmins to Bl layer of same managers.
RPC: added new getAdmins() like method

- Added method getDirectRichAdminsWithSpecificAttributes() to
  VosManager, GroupsManager & FacilitiesManager.

- Added RPC javadoc above other getAdmins() like methods
GUI:  fixed listing of admins to show only direct on "users"

- Show only direct admins when listing users assigned as admins of entity.
- Modified texts on empty admins tables.
Merge pull request #235 from zlamalp/admins

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