moves isd creation into correct py class and adds exceptions to RasterGM (#7)

%include <std_string.i>

%pythoncode %{

    import json    

%}

%include "Isd.h"

%extend csm::Isd {

    %pythoncode %{

        import json

        import numpy as np

            if not isinstance(stream, dict):

                stream = json.loads(stream)

            for k, v in stream.items():

          if isinstance(v, np.ndarray):

              v = v.tolist()

                if isinstance(v, list):

                    for i in v:

                        isd.addParam(k, str(i))

        @classmethod

        def load(cls, fp):

            return cls.loads(fp.read())

  Isd.load = load

  Isd.loads = loads

    %}

}

 No newline at end of file

%}

%ignore CSM_RASTER_FAMILY;

%include exception.i

%exception {

    try {

        $action

    } catch (const std::exception &e) {

        SWIG_exception(SWIG_RuntimeError, e.what());

    }

} 

%import model.i

%import geometricmodel.i

%import csm.i

%include RasterGM.h