GEOMESA-545 Cleanup test raster data in plugin

Test raster images are now created as temp files, rather than being generated in the root directory of the GeoMesa Plugin
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.