Support multiple camera schemes, switchable via the UI

[idanarye]

Maybe something along the lines of:

app.insert_resource(YoleckCameraChoices::default()
    .choice("Top Down", || Vpeol3dCameraControl::topdown())
    .choice("Side Scroller", || Vpeol3dCameraControl::sidescroller())
    .choice("FPS", || Vpeol3dFpsCameraControl::default())
);

When this resource is present, Yoleck will display somewhere a dropdown or maybe radio buttons, where choosing them will remove the old camera controls component (easiest way to do this is just remove all the bundles created by any registered choice) and then add the new components.

Of course - this means that the camera entity will need to be marked with a component.