3819 Better deletion confirmation text for works and chapters

https://code.google.com/p/otwarchive/issues/detail?id=3819

Making deletion work without JavaScript required us to add JavaScript to strip the portion of the URL that was necessary for non-JS deletion. (Is your head spinning yet?) The JavaScript we added included text for the confirmation alert dialogue, but we’d prefer to use text that relates to the action being performed, so the JavaScript now only adds text if none has been specified. Work deletion should now ask, "Are you SURE you want to delete your work? THIS CANNOT BE UNDONE." Chapter deletion (which does not use the JavaScript that enables deletion without JavaScript) will now ask, "Are you sure you want to delete this chapter?"

Please merge this before or for the same deploy as https://github.com/otwcode/otwarchive/pull/1141 so the proper confirmation messages will remain in use.