Interface to be implemented by objects that represent the subscription to an event in Kurento.
Implementers of this interface may be used by the system to track listeners of events registered
by users. Subscribing to a certain MediaEvent raised by a MediaObject generates a
ListenerSubscription, that can be used by the client to unregister this listener.
Luis López (firstname.lastname@example.org), Ivan Gracia (email@example.com)