* Disallow join requests when already part of a cluster
* Remove wipe state when joining, since join can only be
performed from empty state
* When trying to join, only accept gossip from that member
* Ignore gossips from unknown (and unreachable) members
* Make sure received gossip contains selfAddress
* Test join of fresh node with same host:port
* Remove JoinTwoClustersSpec
* Welcome message as reply to Join
* Retry unsucessful join request
* AddressUidExtension
* Uid in cluster Member identifier
To be able to distinguish nodes with same host:port
after restart.
* Ignore gossip with wrong uid
* Renamed Remove command to Shutdown
* Use uid in vclock identifier
* Update sample, Member apply is private
* Disabled config duration syntax and cleanup of io settings
* Update documentation
* Config of node roles cluster.role
* Cluster router configurable with use-role
* RoleLeaderChanged event
* Cluster singleton per role
* Cluster only starts once all required per-role node
counts are reached,
role.<role-name>.min-nr-of-members config
* Update documentation and make use of the roles in the examples
* Subscribe to InstantMemberEvent and start heartbeating when
InstantMemberUp. Same for metrics.
* HeartbeatNodeRing data structure for bidirectional mapping of
heartbeat sender and receiver. Not using ConsistentHash anymore.
Node addresses are hashed to ensure that neighbors are spread out.
* HeartbeatRequest when receiver detects that it has not received
expected heartbeats.
* New test InitialHeartbeatSpec that simulates the problem
* Add/remove some related conf properties
* Add some more logging to be able to diagnose eventual problems
* Explicit config of nr-of-end-heartbeats
* Renamed isRunning to isTerminated (with negation of course)
* Removed Running from JMX API, since the mbean is deregistered anyway
* Cleanup isAvailable, isUnavailbe
* Misc minor
