Added Namecoin Support

The namecoin generation works as expected.

The graphics are a stand in with perhaps just a suggestion of what the color scheme should be. May I suggest you check in the PSD's so people can adjust existing designs to make other altcoin paper wallet options?

I've alphabetized the list of coins. There are lots of graphics missing, including the logo and the finished paper wallet. The front is badly photoshopped and the back is a copy of the Dogecoin one with a hue/saturation adjustment. Please change those.

Anyway, just wanting a nice-looking namecoin wallet and the code is super easy to contribute to, so I did.