Cleverer rp API

[ericboucher]

Ideally the backend accepts a list of service area descriptions. For a full state, this could be as simple as [{'state': 'TX'}], and we could use this information in the cache filename.

Then the backend methods (e.g., fetch) can accept these descriptions and convert them into SQL, etc.

[ericboucher]

Note that we would also be able to switch to GET functions, and then enable caching at the Nginx level.