Clean up Events interface names

[hexus]

DispatchableInterface, ListenableInterface, SubscribableInterface and SubscriberInterface seems all a bit too messy.

It also seems redundant having DispatchableInterface separate from ListenableInterface, I can't remember the reasoning behind this.

Try for the following interfaces:

Dispatchable, Subscribable, Subscriber.

Also while you're at it:

Darya\Http\Session becomes Darya\Http\Session\Php
Darya\Http\SessionInterface becomes Darya\Http\Session