Renamed the dispatcher service to event_dispatcher

Problem/Motivation

The dispatcher service in Symfony is named "event_dispatcher". For better interoperability, using the same name in Drupal would help a lot.

Proposed resolution

The patch renames the service from "dispatcher" to "event_dispatcher" everywhere it is used.

I've also removed this code:

    // Register configuration object factory.
    $container->register('config.subscriber.globalconf', 'Drupal\Core\EventSubscriber\ConfigGlobalOverrideSubscriber');
    $container->register('dispatcher', 'Symfony\Component\EventDispatcher\EventDispatcher')
      ->addMethodCall('addSubscriber', array(new Reference('config.subscriber.globalconf')));

as it is done elsewhere in the same file:

    $container->register('config_global_override_subscriber', 'Drupal\Core\EventSubscriber\ConfigGlobalOverrideSubscriber')
      ->addTag('event_subscriber');