add relay logging (#1263)
This PR adds relay logging to the RelayDetailView.
Features:
* list of events, most recent at the top
* shows changes to RelayConnection's state
* shows changes to network state
* RelayDetailView updates live as lines are added to the log
* logs persisted to disk for later investigation
* line limit prevents unbounded file growth
Here's how it looks when resuming after having the app in the background for a while and the relays need to reconnect:

relays, 5 commits
