* refactors API geometry processing to use GeoJsonValidator and GeometryProcessor just like SimpleGeomForm
* moves cast_to_multipolygon, cast_to_rlp_srid, flatten_geom_to_2D, is_valid_4326 and is_area_valid into GeometryProcessor
* adds changeable SRID to GeoJsonValidator constructor
* updates test data
* updates test cases