database backup foo

database backup foo

no longer dump the full database on each dinstall run. instead we just
save a transaction id. DSA is doing the backup dumps in whatever cycle,
and keeping the WAL stuff around, so we can tell them to get us to
whatever point in our db which we might need, ie. the specific transaction
id.

as those are just 9 bytes per file, and not 4gigabytes, we now also save
wth we have been before and after unchecked runs, which makes our backup
be nearer to actual filesystem state than ever.

Signed-off-by: Joerg Jaspert <joerg@debian.org>
Signed-off-by: Joerg Jaspert <joerg@debian.org>