Recent file locations are a UI thing, not a back-end thing, so remove the table and put it into browser layers.

- the sessionId is no longer in request.session, it's only in request.
- the userId is in request.session.zapUserId
- all known user sessions are in request.session.zapSessionId keyed by the sessionUuid.

Whenever the schema changed, it was attempted to be reloaded, however the DROP TABLE queries failed
because the constraints in reference tables were broken when that happens. Hence the logic to
backup the whole database and start from scratch.

NOJIRA Move DbEnum to shared space. This is being used in the front end for identifying potential flash options

serves as a safety check for studio integration.