[RFC] REST API Support

[Andy Doan]

I'd like to try and get a REST API added to patchwork in a similar form
to Damien's work. Before going too far, I'd like to get input on the
general approach I'm taking. Specific areas I'm interested in are:

 * The choice of Django REST Framework over other options like Tastypie
 * The security model I've chosen for the "Project" model

If all seems kosher, I'll continue down this path of exposing more
items.