Overlays: don't wrap the overlay window, display as-is on top of the cardview

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Overlays: for position only for top-level overlays, and add some debug information

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
OverlaysManager: put the overlay on top of everything, including maximized/fullscreen windows

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>