GEOMESA-558,571 RFI integration and improved RasterStoreTest

* RasterQuery now takes resolution as a double
* RasterFilteringIterator now wired in, with tests
* Noted geohash enumeration issue in one of the tests
* Made RasterTestUtils for common functions in the tests for geomesa-raster
* Improved RasterStoreTest
It's better to add timezone as second parameter when creating a new DateTime instance, like:
def time = new DateTime(metadata.dtgMillis.getOrElse(0L), DateTimeZone.forID("UTC"))