Use a spinner icon instead of the word "Loading" for thumbnails that are
being processed in the background in a batch upload.
Also use morphdom to update thumbnails so we only update the parts of
the DOM that actually changed.
* Make thumbnails on the "My Uploads" page show an icon with an image
count when an upload contains multiple files.
* Make the "My Uploads" page show each upload, not each individual file.
If an upload contains multiple files, they're shown grouped together
under a single upload. This does mean that failed or duplicate uploads
will show up on this page now. This is because this page shows each
upload attempt, not each uniquely uploaded file.
Make media assets show a placeholder thumbnail when the image is
missing. This can happen if the upload is still processing, or if the
media asset's image was expunged, or if the asset failed during upload
(usually because of some temporary network failure when trying to
distribute thumbnails to the backend image servers).
Fixes a problem where new images on the My Uploads or All Uploads pages
could have broken thumbnails if they were still in the uploading phase.
Add a thumbnail view to the /media_assets page. This page lets you see
all images uploaded to Danbooru by all users (although you can't see who
the uploader is). Also add a link to this page in the subnav bar on the
upload page.
Add a view component for rendering thumbnails for media assets.
This lets us properly show thumbnails on the upload listing page and the
media assets listing page, including support for high pixel density thumbnails
and video length icons for videos.
Fixes not being able to see thumbnails on the /media_assets page.
This is mostly copy/pasted from the post preview component. FIXME: don't duplicate code.