Split QWaylandSurface in a model and view fashion

QtQuick compositors already use a view class (QWaylandSurfaceItem),
so add a new QWaylandSurfaceView, which is subclassed by
QWaylandSurfaceItem, and move the view related methods of QWaylandSurface
there. A QWaylandSurface can have many views.

Change-Id: I7e92fe1f7e9d252f5f40a3097feabb5f3318b03a
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>