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
We need to be very careful when defining resolution as double since it is part of rowID. If somewhere we need to calculate a new resolution from given one, like half of existing one, it may potentially results one different from what we want due to accuracy issue in calculations with doubles.