CORE, RPC, REGISTRAR: allow updating titles in name for users

CORE, RPC:
- Added updateNameTitles(PerunSession sess, User user) method which updates titles
  in users name. Implementation is almost same as updateUser() method, but updates
  only titles and also allow to remove title by setting parameter to null.
  Auditer message same as in updateUser() is logged, since it's change of User object.

REGISTRAR:
- If titles before/after name are part of application form, they are stored to user
  during application approval. Values are taken from items linked to "displayName" attribute
  and "titleBefore/titleAfter" attributes, which takes precedence over "displayName".
- Only non-empty titles are stored by application in order to prevent deletion while
  user is logged-in by IDP without his/hers titles included.
- If any of form items can't be stored to DB, exception and wrong value is logged and stored
  for notification to vo manager/user purpose. Password items are not logged.
- Prevent logging unnecessary exceptions when instantiating registrar module.
- Updated logging messages.