Rolling an image back, or restoring a backup a newer release made, ran
older code against a schema it does not know and failed later, far from
the cause. Boot now refuses a database that records migrations this
build does not ship, and the restore check refuses such a backup while
the current database is still in place. A restore also keeps the
database it replaces as data/pre-restore-<time>.db.
Maurice
71a0af02b0