!clu #3599 Use counter in VectorClock

* No reason to use the System.currentTimeMillis base
* Remove the global VectorClock counter completely,
  current count for a node is in the VectorClock itself
Merge pull request #1722 from akka/wip-3599-vclock-counter-patriknw

!clu #3599 Use counter in VectorClock
Merge remote-tracking branch: upstream/master