implement a legistar<->document cloud redirector #151
Description
Our friends at Datamade are interested in taking advantage of the Document Cloud archive we're building. It's possible for anyone to search Document Cloud to get "our" copy of a document originally in Legistar, e.g.
https://www.documentcloud.org/public/search/account:%20%2212872-knight-lab%22%20project:%20%22Chicago%20City%20Hall%20Monitor%22%20Source:%20%22http://ord.legistar.com/Chicago/attachments/4fc6aad9-98e2-41ff-8a24-22ca5b38d49e.pdf%22
But maybe it would be easier for people (and more robust) to have a URL like
https://cityhallmonitor.knightlab.com/leg_to_dc/4fc6aad9-98e2-41ff-8a24-22ca5b38d49e.pdf which would redirect to the DC page (or otherwise make something slightly less dependent on the exact interface between CHM and DC)