Python Bindings for Grandma

This is a new SWIG-based implementation, but the API is (almost) the exact same high-level "grandma" API that I showed off earlier. Here's the updated doc:

http://github.prideout.net/OpenSubdiv/

For now, the build strategy is a hybrid CMake+distutils approach. CMake checks for SWIG and Python 2.7 packages. If they're both available, it spawns Python to look for Numpy. If it succeeds, it adds a "python" target that spawns the distutils script (setup.py). It also adds a command to the install target, which again spawns the distutils script for proper module installation.

I also added copyright headers everywhere as requested.