Remove 3D game functionality from scene page

[johnshaughnessy]

We have regressed the scene page several times over the last few months. It's difficult to ensure correct behavior when loading the 3D game functionality because many files execute functionality on load that is not valid in the context of the scene page.

Until we bundle game functionality more carefully, it will be easier not to run any 3D game code on the scene page. That way, ongoing changes to the engine won't introduce new regressions.