Display consensus bandwidth when available
Right now, vidalia is only ranking and displaying routers based on their observed descriptor bandwidth. In 0.2.1.x, clients began using the consensus "w Bandwidth" lines to choose relays instead of descriptor values. However, the control port was not updated to provide these values until 0.2.2.x. But now that 0.2.2.x is becoming stable, we should use them.
We probably want to keep the descriptor values visible somewhere, but the sorting should probably be based on consensus values.