Moved 2 classes from pypjua.clients.lookup to pypjua.clients.__init__ and renamed pypjua.clients.lookup to pypjua.clients.dns_lookup

darcs-hash:20090127152509-58103-602abe3ee85b557c83be71d4188783461e37b309
fixed GreenInvitation not to implement remote_uri and local_uri since these are now provided by Invitation

darcs-hash:20090127142733-b2873-5aef265ab18e1ee1afd36ea999bbfc04b2aba645