I wonder if there's a good reason to expose the descriptions here.  They don't seem to have particularly meaningful values.  If someone wants to learn more about a particular curve they'll probably have better luck looking around for info on it on their own?  So maybe this should just be a set.

Also I'm not sure this is the right API to expose even the names of the supported curves.  It seems like an increase in the disorder of the module interface.  Curves actually seems more crypto related than SSL.  In the interest of getting some ECDHE support into pyOpenSSL though, maybe the right thing to do for now is just make this private and then sort out the rest of the API details relating to it later.