Ability to georegion code based on a string

This enables directly georegion coding against a column containing zip code strings (eg. "98122") instead of having to geocode the zip code to an additional point column and then georegion coding that column against the region polygon.
Maybe the strictly correct thing to do here is to scope all of the metrics per cache instance? But right now we don't instantiate more than one of each type of cache in the service - only in the unit tests.