Improved dispatch (MTC)

[RichardHightower]

Our dispatch is setup so we can create proxies to local serviceQueues and expose them via REST/Websocket.

The problem is we only handle dispatch from local service queue and REST/Websocket IO, if we wanted to expose a service to another IO channel like Kafka or VertxEventBus, etc. there is no easy way to do it.

I propose the following change.

MethodCall should have a Callback associated with it.
If this Callback is set, this is the integration point for REST/WebSocket/VertxEventBus/ etc.
Instead of using the more hacky way of direct reponsequeue access now.

We may want to make responsequeue and internal concept as well.

[RichardHightower]

This was easier than imagined.