Remove the 'Similar' button next to the source field in the post edit
form. Removed for multiple reasons:
* It doesn't make sense to have to open the edit form to do a reverse
image search.
* The 'Similar' button tries to redownload the file from the source,
which has various problems: the source might have been deleted, it
might have been changed or revised, it might be a format that iqdb
can't handle (ugoira/webm/mp4), or it might otherwise not match the
the actual post.
* The 'Find similar' button already exists in the sidebar and it does
the right thing by using the preview image from Danbooru, which
avoids all the above issues.
The swipe left gesture interfered with scrolling left and right, using
using pinch to zoom, and with copy and pasting text. This gesture wasn't
really necessary anyway, since the back button can always be used to go
back instead.
Refactor things to store information about the current user as data
attributes on the <body> tag rather than as <meta> tags. These <meta>
tags are now deprecated and will be eventually removed.
* Store all of the current user's API attributes as data attributes on
the <body> tag.
* Add `CurrentUser.data` for getting data from the <body> tag, and
use it instead of `Utility.meta`.
* Add `CurrentUser.update` for updating the current user's settings.
* Fix a bug with the user named "Anonymous" not being able to edit notes.
Bug: if you open the tag edit dialog with shift+e, close it, then open
it again, it won't be vertically centered when it opens the second time.
Fix: hide the related tags section *before* opening the dialog, not after.
Hiding it afterwards shifts the layout, which uncenters the dialog.
Initialize the recent tags, frequent tags, translated tags, and artist
tags columns only once, when the related tags section is first shown.
The related tags section is shown automatically when the 'Edit' tab is
opened, or by default on the uploads page.
This fixes the /related_tags.js and /source.js calls being triggered
every time the tag edit dialog box or the 'Edit' tab was opened.
* 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.
Fixes#3807. Drops the TagScript module entirely and replaces it with
a simple call to Post.tag.
Simultaneously fixes#3773 as a consequence of removing TagScript.run.
Post.update already updates data-tags by itself, so there was no need
for TagScript.run to update data-tags as well.
