Add support for referencing a series by the Message-ID of one of its patches in the URL

For example,
http://patchwork.freedesktop.org/mid/1443511466-8017-1-git-send-email-jani.nikula@intel.com
would redirect to
http://patchwork.freedesktop.org/patch/60615/
similar to how
http://mid.gmane.org/1443511466-8017-1-git-send-email-jani.nikula@intel.com
works.

The main requirement would be to have some base URL you could simply append a Message-ID to. And absolutely _without_ the angle brackets < > that patchwork likes to keep around Message-IDs.

This would make it easier to find and pass around patchwork links.