contractcourt: integration aux sweeper to breach arb

Similar to the sweeper, when we're about to make a new breach
transaction, we ask the sweeper for a new change address, if it has one.
Then when we go to publish, we notify broadcast.

server.go

@@ -1187,6 +1187,7 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 			Store: contractcourt.NewRetributionStore(
 				dbs.ChanStateDB,
 			),
+			AuxSweeper: s.implCfg.AuxSweeper,
 		},
 	)