Tidy up TransportImpl
Remove pinned in favour of a genuine membership test.
Ensure AL and LD are quiet when membership is not confirmed by FD.
Pull lifecycle state out into a separate class (NodeState).
Minor adjustment to heartbeat'ing prior to implementing cluster membership change.
Bugfix: TransportImpl can create more than one heartbeater instance.
Codecs support for encoding/decoding a list of InetSocketAddress
Implement membership change support.