Moved MSRP relay usage options to account.nat_traversal

darcs-hash:20090821152629-58252-0166fa8287d66b26262d3436d36bf3248b0bbf34
Fixed nat_traversal setting

darcs-hash:20090822183124-58252-5bbac95f28aa7757b19ef7440288ca4f55351c0d