add a textured sphere8.obj test with obj loader

fix shaders, so that shadowed and non-shadowed are matching
fix registerGraphicsUnitSphereShape API (level of detail), support textured sphere too
add support for textured cube
add start for a Tutorial.cpp

examples/CommonInterfaces/CommonRigidBodyBase.h

@@ -209,9 +209,9 @@ struct CommonRigidBodyBase : public CommonExampleInterface
 
 		btVector3 hor;
 		hor = rayForward.cross(vertical);
-		hor.normalize();
+		hor.safeNormalize();
 		vertical = hor.cross(rayForward);
-		vertical.normalize();
+		vertical.safeNormalize();
 
 		float tanfov = tanf(0.5f*fov);