Preserve scale/orientation of scene input

[pierotofy]

Closes #34

We achieve this by preserving the original scene rotation and training on a translated/scaled version and subsequently restoring translation/scale.

[pierotofy]

One downside is that some viewers will not automatically center to the model (they expect the scene to be at [0,0,0]). If this becomes an issue we can add a flag for optionally keeping the centered orientation.