allow drag-dropping of messages onto NMR endpoints to send messages to ServiceMix NMR/JBI endpoints

See the way the ActiveMQ and Camel navigator objects work. e.g.

com.fusesource.ide.fabric.activemq.navigator.DestinationNodeSupport implements MessageDropTarget and implements this method:

public void dropMessage(IMessage message)

or com.fusesource.ide.fabric.camel.navigator.EndpointNode.dropMessage();

We will probably have to hack the fon-servicemix-facade's ServiceMixFacade API to add a method to make it easy to send to an endpoint; this could involve having to patch servicemix-nmr to add this API to the JMX API.