Update web ui after all channels with peer are closed

[joostjager]

Currently in circuit breaker, peers are only removed from the list after a restart. This issue is about making circuit breaker remove peers on the fly when all channels are closed.

One thing to keep in mind is that there may be custom limits for the peer that is removed. When in the future a channel is re-opened to that peer, it is the question which limit should apply. The old custom one, or should it switch back to default?

Originally reported in #40

[M1ch43lV]

I suggest to keep the information to the old peer after closing the channel. It might be that you or the old peer reinitiate soon a new channel, maybe because it had been force-closed or accidentally been closed.