As the QGraphicsScene overlay does not work for all cards/drivers we disable the possible buffer swap of the qpainter, as this could be a potential source of the flickering. If the painter swaps buffers and we do it again the user will see first the correct picture (first swap) and then something uninitalized (second swap)
-removes all soqtviewer references
-create a quarter adaptor class which implements missing functionality
-adopts freecad code to make use of SoRenderManager and changed View3DInventorViewer interface
