this appears to be okay even though we reuse it between runs without deleting it first.
size of the database appears not to be changing though that could be deceptive
ok, so the estate stores now want their own migration files, but as it
happened the SQL definition were inside the Region migrations.
It seems better/cleaner to keep each 'store' separately updatable.
WARNING: any editing in the middle of the migration scripts (as opposite
to just appending to them) has the potential of messing up updates of
existing databases. As far as I can see, this one is (probably) safe,
the worst that could happen is the EstateStore migration silently fail
if the estate the tables are already there.
Jonathan Freedman