Fixes to DesignManager locking behavior
- handle error, when lock has expired but user left page open, now we prevent submit or apply after another user has started editing
- fix error handling in "edit stylesheet" if for some reason a user managed to open action url directly
- if a user for some reason managed to open action url directly but error handling failed, editing interface was accessed and user id is not identical to lock user id, we disable apply and submit
minor