Create OpenEngine systems in the appropriate manager classes
OEngine::Physics::PhysicsEngine and OEngine::GUI::MyGuiManager are created in Engine. They should be moved to MWWorld::PhysicsManager and MWGui::WindowManager instead. Currently the remains of the MWScene class are blocking the movement of the PhysicsEngine. Therefore this task should not be started before the MWRender refactoring is complete.
Note that OEngine::Render::OgreRenderer is better left in Engine, since OGRE is rather picky about the initialisation sequence and moving it to a later point might cause problems.