Demo Builder + Planes Demo

Simple tool for making demos quickly by manipulating the model directly. It also includes a demo for the recent features added: parallax, move by entity, chase entity.

Probably the best way to begin a revision is to download the PR and launch DemoLauncher. Select PlanesDemo and read the description provided before you actually run it. Then you can deep into the PlanesDemo code to see how it was built using DemoBuilder and how it is linked to Demo Launcher.

Anyway, commit-based revision is also welcome.