Introducing custom and multiple annotation events

[aurasphere]

At the moment, the FbBotmillController annotation takes as an argument an FbBotMillEventType. This works great if a user want to handle a basic event, but what if he wants to define a custom event? I think it would be a good idea to introduce another annotation that takes as argument an array of classes extending FbBotMillEvent. This way you could bot handle custom events and multiple events (without using Java 8 multiple annotations and thus keeping backward compatibility).