Calculate ICE candidate priority according to draft

Ignore-this: e1b14cff10675b74f1719a15ef5ef9cb

darcs-hash:20100209170932-56b4d-f8eb0393b46a790535ac3e33960b09b075d632b2
Changed the way a list is copied to improve the code readability

Ignore-this: 78617c1df2edede20fff4915146d61e

darcs-hash:20100210182021-1e3d8-bdfc1945bd396b67039da9fb1dd2a2bf5970ea5c