Add distutils support for Python interface.
Python extensions can now be built with "sudo python setup.py install"
or "sudo pip install bllipparser" if pip is available. As a result, the
main "make swig-python" target has been removed to avoid confusion (the
others still exist since they're useful for valgrind and other debugging).

Python code has been moved from swig/ to python/bllipparser/
RerankingParser has various cleanups and improvements (plus some new docs).

--HG--
rename : swig/ParsingShell.py => python/bllipparser/ParsingShell.py
rename : swig/RerankingParser.py => python/bllipparser/RerankingParser.py