Allow private media to be downloaded with authentication

This PR adds a view to the template project that can be used to download files with authorisation.

A `Dockerfile` is added too so the uWSGI/Nginx integration can be tested.
FYI, I found nginx to be VERY picky about the url. I had to strip the end '/' off of this line (and the alias I think, though I'm not sure that was required) to get it to work. You might want to just check this one works. Ask the Carlsberg team for help as they already have a working example on test so it should be a simple test