Python plugin mappy writing support

Adds mappy write support and resolves #460

Again pythonbind.cpp has been reordered, looking at pybindgen sources I'm fairly certain this is because [cppclass.get_methods](
http://code.google.com/p/ndnsim/source/browse/pybindgen/cppclass.py?repo=pybindgen&name=#994) uses iterators which are unordered causing methods to be output in random order.
I'll look into reporting this upstream.