Do not set new login from application form when user found while approving.

 - case: user joined identities after sending application
 - notifications: if user known, get login from attribute instead of application (if attribute not empty)
Registrar: do not create application when password reservation fails.
 - GUI: fixed text in exception message
Registrar: notifications to VO admins are now by default 'en'.
 - Optionally based on attribute value for VO/Group.
 - Return RegistrarException to show raw message in GUI when approving application