Lighthouse: Wayland. Make the wayland integration closer to Lighthosue

Lighthouse: Wayland. Make the wayland integration closer to Lighthosue

Today there is a connection between QWidget and QPlatformScreen. So I
added a accessor in QWaylandScreen to get the corresponding
QWaylandDisplay. So now it should be possible to have different
QWaylandDisplays. But also its possible to use the internal Lighthouse
api closer in the wayland plugin if that should be of interest ;)