An installed extension does not receive ApplicationStartedEvent

When an extension is installed it will not receive an ApplicationStartedEvent since this event is only sent at startup so if it count on it to initialize some stuff it's not going to work until it's restarted.

There several possibilities:

• selectively send the ApplicationStartedEvent event to the extension listeners but that's a bit complex
• get rid of ApplicationStartedEvent and make extensions officially listen their own Extension or Component event