Rename fillActive to checkPeers and update

Make it a true "heartbeat" checkup function to ensure the health of the peer collection is good.
Add a status event
Better handle connections that just hang

On connect or disconnect, give peers a few seconds to respond, and if they don't, destroy the connection.
Update Bitcoin example
Don't delay script ending for watchdog timers
During initial launch, aim for the median number of active peers, rather than the minimum
Update for Peers now assemble their own raw message payloads
Add polling for new peers
Delay 'running' state until after first peer connects
Better handle different message data payloads
Handle missing peers on send

If the Peer disappears during figuring out a subset of peers to send to, don't add it to the result.