toolbox (and applethandle?) architecture rewamp

[Giulio Camuffo]

> i think the generic handle plugin and
> should still be limited to Applets.
> the ability to manage normal
> QGraphicsWidgets could be added to your particular iplementation (and you
> would pass 0 as parent in this case)

ah ok, but that way i'd have anyway to reimplement all the logic behind the 
current AppletHandle, which is quite complex.
What i was thinking was to create a base handle class with support for different 
widgets which anyway would offer to an handle developer the same API for the 
applets and the other widgets.

Giulio