GEOMESA-52 A large query-polygon (smaller than the entire world) can work in WFS but times-out in WMS

The problem appeared to be in the enumeration of GeoHashes that
fall within the query polygon (more specifically for the ColF);
when the minimum-bounding GeoHash for the query-polygon became
too large, the enumerator had to step through too many unused
entries before it got to the real query area.

Reviewed by @anthonyccri