* 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.
Change calling convention to explicitly indicate whether the attributes
are for the <th> element or the <td> element. Fixes various cases where
the two were mixed up.
* Fix .col-expand classes not being set correctly on the /post_versions,
/pool_versions, and /notes pages.
* Fix .updater and .updated-at classes not being set correctly on the
/forum_topics page.
* Fix the name param being ignored (noticeable in the post count field
on the /tags page).
* Don't pass empty string when column has no name.
