Implementation of the Multiplexing problem, as well as a new MultiKeyedCommand model and a SplittableCommand model

in here, add
   			private final PendingReply<StatusReply> childReply = new PendingReply<StatusReply>(this) {
				
				public void finalize(StatusReply partialReply) {
					LOG.debug("MSet.split(...).new MSet() {...}.getReply().new PendingReply() {...}.finalize()");
					parent.getReply().finalize(partialReply);
					super.finalize(partialReply);
					LOG.debug("back from super.finalize");
				}
				
			};