[REVIEW] Make controller instantiation customizable

[Greg Brown]

> That's what I was thinking too. If the <param> approach turns out to be taken, then in many ways the ControllerFactory becomes less important because for all those custom dependency injection sort of scenarios, you can actually just use the <param> approach instead (and probably would?).

Maybe. I actually really like the current design and the concept of the controller as the "code behind" the document. It's simple and easy to understand, and addresses most of the use cases I imagine I'd personally want to address as an app developer. Combined with the controller factory, there are quite a few possibilities. The param idea is certainly worth exploring though.

> But ControllerFactory isn't painful, especially if it is just a Callback ;-)

I will refrain from comment on this.  :-)