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.
* Cancel pending ajax requests when mousing out of the thumbnail.
Prevents multiple requests from piling up if the user moves in and out
of the thumbnail before the first request completes. This normally
isn't possible except during slowbooru.
* Show an error message if the ajax request fails unexpectedly.
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.
* Remove .ui-corner-all, .ui-state-highlight, .ui-state-error classes
from notice boxes.
* Use .notice, .notice-info, .notice-error classes instead.
* Replace <p> elements in notices with <div>'s so that we don't have to
work around the `margin-bottom: 1em` from <p> elements.
* Replace <h1> elements in notices with <h2>.
* Standardize info notices to use the same shade of light yellow in the
light theme.
Instead of having custom code check whether the artist name is already
in use, just enable autocomplete on the artist name field. This is an
easier and more robust way to indicate tag name conflicts.
* Rename Upload#download_for_upload to #get_file_for_upload.
* Fix #get_file_for_upload to raise error if no file or source url was given.
* Fix javascript upload validation to disallow submitting form if file is
not present and the source is not an url.
Bug: in the modqueue, if a user does a detailed rejection of one post,
then tries to do a detailed rejection of another post, the form will
still be filled in with the rejection message from the previous post.
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.
