Vacuum the raw.db occasionally

[james-antill]

Not a priority, but there is a vacuum command in the git repo (although not installed) and you can run it manually within a couple of hours.

Even though the trim command does reuse space it's far from perfect (raw.db seems to grow quite a bit the first couple of weeks, and then I think tapers off -- but still grows slowly without a vacuum).

Should probably have it run in cron on the 31st (so every two months or so).