CORE,RPC,REGISTRAR: allow updating titles of 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.