[Bf-codereview] Derivative filtering for multires baker (issue 13778045)

[brechtvanlommel at gmail.com]

I think RPT_INFO would be the appropriate way to report the scale. We
don't really have a good mechanism for this kind of thing, but it seems
the most logical solution.

Further looks good, except the UI, I would make this another bake type
even if the implementation internally is based on displacement.

https://codereview.appspot.com/13778045/