[Bf-python] New Constants proposal

[Ken Hughes]

I decided to try implementing the new PyType Constants to see how they 
might work and how they would perform.  This is based on some of the 
ideas I had for bitfields; I didn't try implementing that yet, but what 
I've worked on so far could be extended pretty easily to cover them as 
well.

The description is here:

http://wiki.blender.org/index.php/BlenderDev/Bitfields

(Ignore the name in the URL: I just added constants to the old proposal)

Ken