Allow admins to delete media asset files.
This only deletes the image file itself, not the upload or media asset record. The upload will still
be in the user's upload list, but the image will be gone. The media asset page will still exist, but
it will only show the file's metadata, not the image itself. We don't delete the metadata so we have
a record of what the file's MD5 was and who uploaded it, to prevent the file from being uploaded
again and to take action against the user if necessary.
* Add a "Size" menu to the My Uploads / All Uploads pages to allow
changing the thumbnail size.
* Make the My Uploads / All Uploads pages use the same thumbnail size as
the post index page.
* Change the "Gallery | Table" links on the My Uploads page to icons.
* 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.
A MediaAsset represents an image or video file uploaded to Danbooru. It
stores the metadata associated with the image or video. This is to work
on decoupling files from posts so that images can be uploaded separately
from posts.