Added SWIG typemaps to convert Python primitive types to SNAP.

Using SWIG typemaps, we convert the Python primitives, a list or a string, to C++ functions, while using the SNAP for the backend.  This also works for outputing Python primitives.

So, here is a comparison of the two methods, 2 and 3.  Also, there is a Python optimization in C, called, PySequence_Fast_GET_ITEM, which I used for a second version of 3.  This is less secure in that I am not checking each value to make sure it's an integer, but it's significant significantly faster. This is in the snap.i interface file.