Adds an object-oriented light representation. #142
Deletes the typedef t_nodeIter that isn't used anythere.
Adjusting the light representation to fit the lightingsystem class and implementing the necessary pure virtual functions like boundingBox() and draw(), without doing anything yet in draw(). #142
Renames the light structs in order to avoid the same names with the classes. #142
Alters doubled code to a template in scenetraverser and deletes the scenetraverser.cpp in CMakeLists.txt.
Deletes the scenetraverser.cpp, because it isn't needed anymore since changing to an template methode in the header.
Adds a new visitor for pretraversing the scenegraph and collecting the light data and setting the camera views. #166