Changed load system to centralize load on a class.
Moved object list to its own file, renamed it to HandlerList
Create unit test cases for HandlerList
SceneNodeHandler renamed to SceneNodeKeeper
RenderWorld renamed to MapManager
Simplified MapLoader rule, MapManager got a better name.
Restored terrain support
Rigid body is now a moveable class.
Added back support for RigidBody on static world
Removed tile system;
Merge branch 'feature/load_redesign' into develop