InlineMediaDownloader: Also download flickr images

See #222
InlineMediaDownloader: Hide thumbnails for failed downloaded images

If the intermediate website can't be loaded for some reason, just hide
the thumbnail.
InlineMediaDownloader: Close the streams

We were leaking the fds from *all* the media, up to 3 of them per image.

This fixes #235 for me.
Merge branch 'master' of https://github.com/baedert/corebird
Merge branch 'master' into main-widget
InlineMediaDownloader: Also close animation streams

Again #235