add scene graph by iv-string

[microelly2]

Thank you,

how comes your commit into FreeCAD master?
Good to know that there is a common way to use the iv-syntax.

[looo]

Simply clone, and run "sudo python setup.py build/install". Mybe you also have to delete the default pivy, because manual installation will install in /usr/local/lib and the apt-installer places pivy in /usr/lib/.... .