* Changed router interface to return Advertisement channel
* Added default gateway route to the routing table if supplied
* Watch table for updates and advertise to the network
* We hash the routes on 3-tuple (Destination, Gateway, Network)
gw has not been initialized; it was basically an empty string and only
got populated by Sprintf-ing the addr:port IF the port has been set.
This commit sets the gw to node.Address to it's never an empty string.
