GEOMESA-213 GeoHash corner cases

* GeoHashes now must be inside the rectangle [-180.0, 180.0] by [-90.0, 90.0].
* The top and right corners of the world rectangle are now 'nudged' back in rather than wrapping.
GEOMESA-273 Id queries do not work

Intercept ID queries and go straight to the
record table
GEOMESA-277 Refining DensityIterator Stacking

* Refactored the DensityIterator to be separate from the SFFI.
* Moved the DensityIterator to run after the SFFI.
GEOMESA-282 Change the namespace to org.locationtech.geomesa

Included some import re-ordering.