[C++-sig] Boost.Python V2: list implementation

[David Abrahams]

I have just checked in the implementation of the Python list class wrapper!
Tests in libs/python/test/list.[cpp/py].

This opens up the possibility of implementing the other built-in types:
tuple, dict, str, int_, long_, et. al.  This is another of those "fairly
mechanical" tasks with which I would really appreciate having some help.

The interface design follows the following protocol:
I did:

>>> help(list)