* Remove the PostRegeneration model. Instead just use a mod action
to log when a post is regenerated.
* Change it so that IQDB is also updated when the image samples are
regenerated. This is necessary because when the images samples are
regenerated, the thumbnail may change, which means IQDB needs to be
updated too. This can happen when regenerating old images with
transparent backgrounds where the transparency was flattened to black
instead of white in the thumbnail.
* Only display one "Regenerate image" option in the post sidebar, to
regenerate both the images and IQDB. Regenerating IQDB only can be
done through the API. Having two options in the sidebar is too much
clutter, and it's too confusing for Mods who don't know the difference
between an IQDB-only regeneration and a full image regeneration.
* Add a confirm prompt to the "Regenerate image" link.