Badpenny Part III

This adds the ability to register and run periodic tasks, as well as a cleanup task that serves (if nothing else) as an example.
Putting it in its own table doesn't help searchability.  And RDBMSes don't support arbitrary keys.  I don't know what "smart data concat stuff" means.

I'd be happy to rip this column out entirely, if that would make you feel better.  I don't see much use for it.