ref #77 Merge master into PathTracingGPU_77

use new scenegraph for fetching geometry data

Conflicts:
	apps/cgsee/painter.cpp
	libs/core/CMakeLists.txt
	libs/core/camera.cpp
	libs/core/group.h
	libs/core/polygonaldrawable.cpp
	libs/core/polygonaldrawable.h
	libs/core/polygonalgeometry.cpp
	libs/core/polygonalgeometry.h
	libs/core/scenegraph/group.cpp
	libs/core/scenegraph/node.h
ref #77 merged updated shaders to pathtracer with scenegraph2