Start to use the media_id in "admin" URLs.

Start to use the media_id in "admin" URLs.

We have a bunch of URLs that are more for internal use. At
least they're definitely not intended to be posted
somewhere for long term useage.

When those things affect a media, it's much better to
reference the media by its id. This can't change, ever.
This is better for races.
Like someone posting a comment while the owner
corrects a typo in the slug.