This reverts commit f65830ba.

Laurent Bachelier authored Jul 15, 2018 and Romain Bignon committed Sep 17, 2018

- Introduce more swear words to represent the diversity of the English language
- Upgrade outdated insults
- Only wish harm on objects (though webdevs barely qualify as human)

Did this mostly because the first video had an issue, it was first
in the search results but deleted (the page was "410 Gone").
But this ends up testing more videos anyway.

There is now a "latest" collection (or "latest_nsfw").
The feature didn't look much used, since it didn't work on many
backends.
Using collections will make it easy to support other things
like most viewed, featured, etc.
As a bonus, I added tests for every backend with the feature.