Issue 4067: Respond with 404 instead of redirect: chapters, users

https://code.google.com/p/otwarchive/issues/detail?id=4067
The wording on this one sounds a bit awkward - maybe "Couldn't find chapter '#{params[:id]}' belonging to work '#{params[:work_id]}'"  (please also note the single quotes around the params as that's what we've used in these messages elsewhere).