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
There is some redundant code in each of the tests that could be factored out and made into a function to simplify things.