Physics / Scene module updates

Only major thing is I removed Physics from the Scene, it's better IMO to be able to setup Physics within the game module, then apply it to objects from there, e.g.

     // game.js
     this.physics = new Physics();
     this.player = new Player(...);
     this.player.setPhysics(this.physics);

Etc... When viewing the Scene code, it looked like the only purpose Physics had in it was to set it to the Player. Maybe there's other reasons!