RFC Extract Geometries, Widen Geohash coverings, and minor refactoring.

This branch: 
 * widens getUniqueGeohashSubstringsInPolygon to accept Geometries rather than merely Polygons.
 * pulls geometries from actually Filters rather than using FilterToAccumulo.
 * pulls out some of the Filter processing as a trait.
If I don't have to, why should it? 

In full disclosure, I didn't spend much time on style.  I'm looking for the 10k view.