Patch for some issues.

Fix the polyhedron_multmatrix4() method.
Add GIL for multithread support.
Change the extrusion method to support arbitrary extrusion directions and 3d polylines.
Merge branch 'master' of https://github.com/jamesgregson/pyPolyCSG

Conflicts:
	.gitignore
	setup.py
	source/python_wrapper.cpp