Improve JavaDoc for ways to listen to events

It's easy as a beginner to miss that there are both setOnXxx(hander) and addEventHandler(x, x). This can easily be improved by at both sites link and explain the other version. There should also be an explanation why there exist two different ways, how they relate and when to use which version.

Also, I think it would be good to list all the EventTypes in the JavaDoc for addEventHandler(x, x). Or at least link to a place where they all are. Now I can't find a good way to get a hold of what I can listen to since it's not a class hierarchy.