Add cross-process rendezvous capability

It would increase the utility of Byteman if the tool supported cross-process rendezvous. Currently, two or more threads can be coordinated within a single process. However, some testing scenarios require the coordination of multiple processes. This would be especially useful for reproducing concurrency issues in cluster-aware software, where two installations cannot be placed easily into the same JVM (JBM/Hornet Queue).

Also, a utility to clear the rendezvous in order to free waiting threads after failed test iterations would be helpful. This will reduce test cycle time because some processes may not need to be rebooted to reset the test.