Vislab export functionality
I have outsourced the OpenSG (VRED) export functionality to a submodule in ThirdParty/VtkOsgConverter. I have also implemented Fbx (Unity) export functionality in the same way as a submodule in ThirdParty/VtkFbxConverter. Both functionality is used in the Data Explorer and is optional. Dependencies are the OpenSG-1.8 libraries and the FBX SDK version 2013.1.