Python wrapper for RPi added

Hi,

python wrapper for RPi added. 
- boost.python lib used
- some pythonizing done
- build: ./setup.py build
- install: ./setup.py install

a RF24 shared library containing RF24 module (wrapper) is generated and made available for python. It depends on regular RF24 shared library for RPi.
Usage - see examples.

Regards,
mz-fuzzy