new C++ demo: realtime.cc (real-time scene viewer using SDL) Quaternion, Camera::rotate and Camera::move replace all printf's with infomsg wrapper don't allocate memory in Raytracer::render, just blindly write to provided address don't creat Container object in Raytracer, let user do it

demos/*.png
demos/kdtree.obj
demos/*.ply
ccdemos/*.png
ccdemos/spheres_shadow
ccdemos/realtime