database schema for AS bookkeeping

the "as-lib" work will need to store data in the database, namely:

- cooldown tracking (when did this group or policy last get executed)
- perhaps rolling-update stuff (though maybe we have enough information in the properties and sub-template for this)

These tables should be created. If the "as-intermediate-resources" BP gets implemented, they should live in the main heat database, but when the separate AS API is implemented they should live in a separate database that's entirely the domain of the autoscaling service.