Sort out the thumbnail situation

[rebeccacremona]

1. Are we being affected by Serious performance issues in 12.2 (AWS S3) jazzband/sorl-thumbnail#351? (Surely yes, but lets investigate the extent.)
   2) What's up with thumbnails and redis on heroku?
2. What is the point of using thumbnails in the logo carousel in the first place (rather than sizing the images appropriately when we create them)?
3. If we were to remove the logo carousel, or make them regular images instead of thumbnails, would it be worth keeping/fixing the sorl + redis code, given issues Thumbnails for each link on the my links page #821, If we add back in Thumbnails, display on delete confirm screen  #1146, and Add thumbnails on archive capture #1910 express a pretty strong desire for thumbnail images of captures (once a feature of Perma, not presently a feature)

[rebeccacremona]

The plan, per in-person discussion:

We are going to replace the carousel with a different, less complex design element. @anastasia is going to take a swing at coming up with something (a list of a few prominent registrars? an image? something else?)

With that in place, we are going to rip out the existing code/settings/etc. related to thumbnails, and as much image-processing software as we can.

And then, if we end up adding thumbnails of captures later, per the issues referenced above, we'll research which libraries/combination of libraries we need at that point. It might look just like what we ripped out, but it might not: we can reference the commit that removes the code in the thumbnail issues, to help make sure valuable knowledge isn't lost.