The great link migration

Use Site.TinyName in the various URL paths, because it's typically shorter/less ugly/easier to remember/whatever. All old URLs should be correctly redirected to the updated paths, with the minor exception of multisite CSV downloads where we never cared about the site name to begin with.

Also made the redirect from /sitename to /sitename/queries a little more sane, since pages that are not valid sites should just 404 before the redirect.