* Add always zoom invariant and always on top rendering to
ViewProviderDatumCS
* Add a new utility class AxisOrigin for more efficient axis rendering.
Also exposed to python.
* Change ViewProviderPlacement to use AxisOrigin for rendering.
A single instance of AxisOrigin is shared by all
ViewProviderPlacement. Selection context is used to distinguish among
different instances.
+ fix SoAutoZoomTranslation and SoZoomTranslation to get correct scaling factor
(do not rely on active view because this can be the wrong one and thus delivers wrong results)
-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