Deprecated Dispatcher::setListenerFilter method.

I realised that this method was unnecessary and we should be delegating that operation elsewhere and returning the resulting array in the second argument of `setListener`, for example:

```php
$dispatcher->addListener(
    new ContentListener,
    array(
        'onBeforeContentSave' => Priority::NORMAL,
        'onAfterContentSave' => Priority::NORMAL,
    )
);

// Alternatively, include a helper method:
$listener = new ContentListener;
$dispatcher->addListener($listener, $listener->getEvents());
```