Custom "Stage Close" behavior

[clisztian]

Greetings, Fantastic job on the customStage project. Was definitely needed in the javaFX world.

One thing you might want to implement is to allow the user to set a custom behavior when closing the Stage. If I have multiple windows, and I just want to close one, there is no access to define this behavior, as you simply use the Stage System.exit(0), and thus closes the entire application down. Perhaps having an option close/hide might be better for some cases.

Unless I'm missing something... Thanks and cheers