Adding Scenes

We are adding Scene as a separate component, so we can organize things for transitions in particular, where we plan to do use render-to-texture techniques.

Things like the Locator and Timer may get moved into the Scene, so it stays a self-contained unit, and makes tearing down a Scene simpler.

The Install Pipeline for a Scene will use composite pattern, so Scene will delegate Resource Load, Render, etc. to its component GOs. Before calling install() the Scene is populated with its components.

Starting/Transitioning a Scene will be a specific method call on the GameCycle class. This will post a message to the apartment to pick up processing. Expected use is to call this method from the loaded() callback for the Scene.