GUI needs extended View/model interface

[JulesGosnell]

I'd like to take a GUI View attach a Model, see the data, then detach that Model and attach another...

However - The GUI View requires Metadata to drive e.g. the number of columns in a Grid.

This needs to be returned by Model.registerView.

The View needs to be responsible for this call, since it needs to take the returning Metadata and Data and update itself. At the moment, View does not encapsulate the making of this call, resulting in lots of ugly update code everywhere...