Allow for listening for parent classes or interfaces

[inxilpro]

Right now, Verbs looks up hooks specifically by the class name. So if you have a listener that listens for the root Event class, or an interface that your events implement, Verbs will not know to trigger it. This PR adds support for any of those scenarios:

interface IsSpecialEvent {}

class NormalEvent extends Event {}

class SpecialEvent extends Event implements IsSpecialEvent {}

class MyListener
{
    public function listenForJustNormalEvent(NormalEvent $event)
    {
        // Only gets triggered when the `NormalEvent` class is fired
    }

    public function listenForAnySpecialEvent(IsSpecialEvent $event)
    {
        // Gets triggered when any event that implements `IsSpecialEvent`
    }

    public function listenForAllEvents(Event $event)
    {
        // Gets triggered when on all events
    }
}