GEOMESA-584 Refactor Geoserver registration code to add "resolution" coverage parameter to layer

When making the POST to the GeoServer rest client, a resolution coverage parameter is added with
a default value of 1.0. This fixes a NullPointerException that was sometimes encountered when registering
a layer with Raster ingest code.
No, it's just the default value until we start using the accResolution parameter here https://github.com/locationtech/geomesa/pull/399/files#diff-9bbae2a0a5c1d3adcc7c1166c7a1109dR41