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.
Move PostPresenter#categorized_tag_groups to TagSetPresenter#split_tag_list_text.
This allows split_tag_list_text to reuse the same set of tags already
fetched by the tag set presenter for the sidebar.
This avoids a memcache call to get the tag categories when rendering the
tag string for the post edit form.
Refactor tag_list_html, split_tag_list_html, and inline_tag_list_html to
take the `show_extra_links` and `current_query` options explicitly,
rather than implicitly relying on CurrentUser or taking `params[:tags]`
from the template.
* Move the limit:<n> / order:random metatag parsing from the controller
to the post set.
* Introduce `Tag.has_metatag?` and use it to parse these metatags
instead of using a regex (#2894).
* On posts, automatically trigger "Fetch source data" when clicking the
Edit tab, instead of triggering the artist finder button. This way we
find both the artist and the translated tags in one ajax call.
* Remove the "Artist" finder button next to the source field. This isn't
necessary given that "Fetch source data" finds the artist itself.
* Remove the /artists/finder.json API endpoint. This is no longer used
after removing the "Artist" finder button.
* Consolidate blacklist css in one file.
* blacklist box: fix tag colors not dimming on hover.
* blacklist box: allow middle clicking on tags to open in new tab.
* /wiki_pages: move blacklist controls to top of tag sidebar.
* /wiki_pages: fix missing "disable all" / "re-enable all" buttons.
* Don't show 'Flag' option on already flagged posts.
* Drop flag/appeal link show/hide Javascript (did nothing, links were already shown/hidden in html).
