[widgets] Window modes

We currently have gap in the Packaging spec wrt window modes of widgets.

We began to define the following, but did not get very far:

* window: appears with chrome around it.
* fullscreen: No chrome, not resizable.
* floating: No chrome, floating window (dragable, author re-sizable via code).
* hidden: No visible.
* default: Let the implementation decide.

I'm not sure how to proceed with regards to window modes. We need to
define them somewhere, but they are going to hold up the packaging
spec. I think the Packaging spec should only list the name of the
modes, as they are needed by the widget element's mode attribute, but
not their behavior/rendering, which should be specified somewhere
else... but I don't know where.

Kind regards,
Marcos

-- 
Marcos Caceres
http://datadriven.com.au