Add tile log analysis

This adds a process which runs a cron job processing the tile logs into summaries of "z/x/y count" daily.
> Might it be better to build these into packages, either hosted internally or using something like launchpad?

I don't like packages/PPAs for this stuff - it makes it much harder for an observer to figure out how the system works, and the creation of packages is often not code-driven, so it becomes hard to reproduce and/or handover in the future.