* The problem was a race caused by HeartbeatReq sent out, and
the watchee terminated immediately. That caused the RemoteWatcher
peers watching each other without any other watch registered.
It is racy.
* Instead of one-way heartbeats from the side beeing watched I
changed to ping-pong style. That makes the problem go away
and simplifies a lot of things in RemoteWatcher.
* For graceful leaving and remove it should still be possible to
communicate with the node after cluster removal.
* Otherwise the hand over in cluster singleton would break, for
example.
* Also, skip selfAddress to avoid generation of AddressTerminated
for the own node when removed from cluster.
* RemoteWatcher that monitors node failures, with heartbeats
and failure detector
* Move RemoteDeploymentWatcher from CARP to RARP
* ClusterRemoteWatcher that handles cluster nodes
* Update documentation
* UID in Heartbeat msg to be able to quarantine,
actual implementation of quarantining will be implemented
in ticket 2594
