[REVIEW] Make controller instantiation customizable

[Greg Brown]

> Yeah but you require me to make up an classpath to make to look up
> succeed which when you'd give me a way to intercept the lookup where I
> simply return the files content (or URL) would not be needed!

I'm afraid I still don't understand. You're not "making up" a classpath - you have defined it as "/my/package/test/". Are you suggesting that FXMLLoader should allow you to redefine the meaning of the classpath? If so, that seems *really* confusing.