GEOMESA-552, 553 Refactor GeoMesaCoverageReader to utilize functionality in geomesa-raster, create class to hold GeoMesaCoverageReader parameter values

Removed redundant code in GeoMesaCoverageReader to instead use code in the geomesa-raster project. Also moved code from geomesa-plugin to geomesa-raster to better structure and organize the project. Added a class to store GeoMesaCoverageReade GeneralParameterValues to aid in queries for raster images.
Is the resolution of the WCS request (what is returned) being conflated with the resolution we wish to pull out of Accumulo? I don't think that's what we want here. At least not yet. It might be wise to define a "query resolution" which is the ultimate target resolution of the request, and the "source resolution" which is what the Accumulo query will fetch. Down the road we want those to be as close as possible.....but we should not worry about that now.  
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[picky] long line