added the necessary interface code.
* Initial port of MemMap class from python to C++, together with
python interface. Hopefully maintenance of MemMap can be kept
in C++ for speed if possible.
Al
no method as an error.
* Got python interface code to the point that python classes can now
access the C++ attributes of a Thing.
* Split the python interface code into separate files depending
on the type of C++ class the code relates to.
Al
