fixes solid extrusions and enables GhPython usage

IsObjectSolid was not working for extrusions and also not in GhPython.
This should fix it.

Ref http://www.grasshopper3d.com/forum/topics/difference-between-gh-python-component-and-python-in-rhino
Merge branch 'master' of https://github.com/mcneel/rhinopython