Comment 1 for bug 1272122

Setting this one to "Snack-sized". I think it'd be a pretty standalone bit of work, and probably quite achievable since we already require some image processing libraries.

There are two workflows we'd need to support:

1. Rotating an image that's already been uploaded, via the Content -> Files page.

2. Rotating an image as it is being uploaded, i.e. via the Pieforms filepicker element on the Image Block or elsewhere.

It'll be tricky to think of a good interface for #2. We don't want to further complicate the filepicker by adding a pair of great big "rotate?" buttons that will always take up space but only be used 5% of the time. Maybe it would be better to just implement workflow #1...