Adding message forward capability to vertx-core

Simple functionality for message forwarding. Note, this will probably require a bit more work, but for now the basic functionality is in place. See MessageTest unit test for how it works.
Right, but I thought it would be good if I went through the whole thing of creating verticals, deploying them, setting up etc. It's verbose, but I didn't think it was that much. Also, this is the first iteration of Message testing which we never had before so I can clean it up as we move along.