Int 3460: Support output-channel when an AbstractCorrelatingMessageHandler is 'ref'd by a Service Activator	

INT-3460: Support output-channel when an AbstractCorrelatingMessageHandler is 'ref'd by a Service Activator	

* allow AbstractCorrelatingMessageHandler's output referenced by service-activator output-channel
* add test 
I think it has to be more generic:
```
The base {@ AbstractMessageHandler} implementation for the {@link MessageProducer}.
```
And that's all. Without any notes about terget implementations.