* added Debug\TraceableEventDispatcher (originally in HttpKernel)
* changed Debug\TraceableEventDispatcherInterface to extend EventDispatcherInterface
* added RegisterListenersPass (originally in HttpKernel)
* added TraceableEventDispatcherInterface
* added ContainerAwareEventDispatcher
* added a reference to the EventDispatcher on the Event
* added a reference to the Event name on the event
* added fluid interface to the dispatch() method which now returns the Event
* added GenericEvent event class
* added the possibility for subscribers to subscribe several times for the
* added ImmutableEventDispatcher