decrease build verbosity
make the demo do something again
depend on qtbase, not import it
keep the sceneRect Null if there are no items yet (during view resize)
rescaleMode() should return RescaleMode, not bool
layer geometry now defaults to sceneRect, falling back to 600x400 when
Null. If the layer has a parent, we throw a warning (the parent is
responsible for layout). If the scene has a view in geometry rescale
mode, then the geometry is taken from the view dimensions.