CORE: updated javadoc

- Fixed many typos in our javadoc.
- Removed some unecessary lines from source like 'empty comments'.
- Removed historical and unused class ClustersManagerImplApi.
CORE, BEANS, GUI: renamed exception to fix spelling

- Renamed: ServiceUserOwnerAlredyRemovedException
  To: ServiceUserOwnerAlreadyRemvedException

- Use fixed exception in CORE and GUI
Merge pull request #159 from zlamalp/spell

CORE, BEANS, GUI: updated typos in javadoc
GUI: prevent service users to log-in to GUI

- Display error message and stop loading GUI
  when connected user is of Service type.
Merge pull request #160 from zlamalp/serv

GUI: prevent service users to log-in to GUI
GUI: redesigned connection lost widget

- Display "re-connect" button for manual checking.
- Still checks automatically if connection is back online.
- If manual check fails, display message about browser refresh.
- Updated implementation of Confirm widget
  (added more native DialogBox settings).
Merge pull request #163 from zlamalp/refresh

GUI: redesigned connection lost widget