Tweaks to User; Space load problems now tolerated

The main change here is some try/catches added so that trying to load an
inconsistent Space no longer crashes all the way up to the UI.  Instead,
we quietly ignore the problematic Things, and log the Error.  (A bit
dangerous, but necessary from a time perspective.)

Beginnings of implementing Identity correctly, but just the beginning.

Beginnings of email, but again, just the beginning.
Another couple of inconsistency catches

Cope with not finding the Model for a Thing: fall back to using UrThing,
and log an error.
Fixed some problems with checkbox fields
Refactorings to simply Modules
More refactorings

Main focus here is getting a more guaranteed initialization order.  Most
of the action in Modules now happens during init and system object
creation; once we have DependsUpon, those can be controlled
appropriately.