`examples/libraries/overlayUtils.js` allows you to manage overlays in an
object oriented manner. Instead of:
var billboard = Overlays.addOverlay("billboard", { visible: false });
...
Overlays.editOverlay(billboard, { visible: true });
...
Overlays.deleteOverlay(billboard);
You can now do:
var billboard = new BillboardOverlay({ visible: false });
...
billboard.visible = true;
...
billboard.destroy();
