Progress towards initial Notifications.

Wound up implementing UserCache, largely by accident but it's been on the
to-do list anyway.
Finally replaced the blocking wait for the User record with a proper
Async. For the first time ever, this code is now right.
Begin to display Notification Alert. DB CHANGE!

IMPORTANT: note that 8.sql will need to be applied to the system DB.

Displaying the bell icon. Not actually hooked up to the actual number of
new notifications yet, but we'll get there soon.
UI now gets the number of notifications from the back end.

Still mocked up, but from further back in the stack.
Pushed things all the way to the Persister, finally.
Made the message pathways a little more correct.
We are now actually evolving up the User Notifications table.

This involved many incredibly stupid bugs due to the duplicate code between
Space and User evolution. Really need to refactor this.
We now load the current Notifications when we start the UserSession.

Of course, we aren't *creating* any Notifications yet. But we're close.
Finished hooking up the pieces to send a System Message.

Worked the first time, too, which is a fine change of pace.
Bugfix: it appears that a MySQL SMALLINT is still a Java Int.