LevelManager Update - Remove lvlEnded Signal. Add Nape Teleporter PhysicsObject.

I'm suggesting the removal of the `lvlEnded` reference and callback in the LevelManager Class. This Signal can be created and managed by the user. The `_onLevelEnded` method is empty and private and therefore serves no purpose. However, this can cause issues if the user created Signal dispatches with an object:
```
lvlEnded = new Signal(SomeObject);
lvlEnded.dispatch(new SomeObject());
```
In this case, because the `_onLevelEnded` method expects `0` parameters, an error occurs. 

Second, I've created a Nape version of the `Teleporter` physics object. This is simply a port from the Box2d version.