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 
Change comment to `AMPMH`.

We also need logic in `AbstractStandardMessageHandlerFactoryBean` line 80 to look for `AMPMH` instead of `ARPMH`.