At present, there's an option to allow users to scale their uploaded images.
However, this is unnecessary clutter because I want to automatically resize the
images (to save storage space) but not let users see this. So it would be good
to have two separate permissions:

1. "Allow users to resize uploaded images"
2. "Automatically resize all uploaded images to: [max width] and [max height]"

If the first preference is "true" then this would override the second
preference, so that users can still choose their own uploaded size if required.