Improvements for starting/killing nodes

* KillStage with delayExecuting can be followed with KillStage with waitForDelayed which will wait until the execution is finished
* ParallelStartKillStage can delay the start/kill, also tearDown is supported
* StartClusterStage has configurable cluster formation timeout (waiting until the number of members gets to the expected value)
* fixed SLAVE_PARTITION for JGroups >= 3.3.x