UI should detect when it is out of date, and automatically reload

(Bug, Closed -> Fixed, Priority: High, Test Status: No automated tests yet , Reported By Justin du Coeur, )
User Interface
Summary: Now that we're API-based, it's really important that we detect mismatches between the front and back ends. Kate hit a mysterious error because the front end was out of date.
We should have the protocol always send the current version number in the API envelope, and have the Client check that. If it is out of date, force a top-level reload.