[REVIEW] Make controller instantiation customizable

[Gaja Sutra]

> OK, thanks. I believe I understand the value now. This would allow a 
> caller to apply some type checking on values that are used to 
> pre-populate a loader's namespace, and would also allow a caller to 
> pass arguments to an include (something that isn't currently 
> supported). Seems particularly useful when creating bindings, as in 
> your example below. Not sure what other uses there might be.
>
> However, I see this as something that would complement the existing 
> controller support rather than replace it.
I agree completely with you, the possibilities of controller and 
ControllerFactory will always be useful.
Parameters are simplifying the controller, removing some Java 
boilerplate by improving FXML.

I hope personnally some simple controllers will become empty 
(particularly for small includes), with their job taken by declarative 
and toolable code (like parameters and the more complex idea of SCXML), 
but this is only a personal hope from an XML man (or an XML heavy 
elephant). In current state of tools, this is not an hope for tomorrow, 
for many controllers (given Scene Builder does not have even a public beta).