IVerbHandler provides the method that all verb handlers need to implement.
The concrete implementation of this interface would provide the functionality
for a given verb.
This method delivers a message to the implementing class (if the implementing
class was registered by a call to MessagingService.registerVerbHandlers).
This method delivers a message to the implementing class (if the implementing
class was registered by a call to MessagingService.registerVerbHandlers).
Note that the caller should not be holding any locks when calling this method
because the implementation may be synchronized.