[form controller] clear caches in case some attribute participating to the rest path has been modified, avoid redirection to a no more existant page (fix #753567)

i18nupdate

[form] fix validation error handling * type when possible ValidationError raised by the edit controller * don't rely on repository to check required field * turn css class used for field error message to errorMsg to avoid confusion with the error class added to input * fix css when errors are added by the form renderer * fix form renderer to add the error message