* Replace the .category-N CSS classes on tags with .tag-type-N. Before
we were inconsistent about whether tag colors were indicated with
.category-N or .tag-type-N. Now it's always .tag-type-N.
* Fix various places to not use Tag.category_for. Tag.category_for does
one Redis call per tag lookup, which leads to N Redis calls on many
pages. This was inefficient because usually we either already had the
tags from the database, or we could fetch them easily.
* When creating an artist by clicking the '?' next to the artist tag in
the tag list, prefill the new artist form by finding the artist's last
upload and fetching its source data.
Previously we filled the urls with the source of the artist's last
upload, which was wrong because it was usually a direct image URL (#3078).
* Fix the other names field not escaping spaces within names to underscores.
* Fix the other names field being potentially prefilled with duplicate names.
Refactor the /related_tags.js call so that when the "Related tags"
button is clicked, it only replaces the columns that actually changed,
not the entire related tags section.
This avoids rebuilding the Recent / Frequent / Translated Tags / Artist
columns every time the "Related tags" button is clicked.
Instead of calling /sources.json and rendering the "Fetch source data"
box client-side in Javascript, call /sources.js so we can render the
html server-side.
Also makes it so that using the bookmarklet always triggers async upload
preprocessing. Before it was only triggered when the source passed a
dupe check, but that check was inaccurate (#3873).
* In the `Fetch source data` box, list the Danbooru artist tag(s) that
were found beside the artist name.
* Unify `Fetch source data` code that was duplicated between the
uploads page and the post show page.
