Fix images url and add redirects for wiki

Images location from a url perspective is /w/images, not /images.
Also, add redirect from /article to /wiki/article.

Change-Id: I63f29a5c3e66e3a3e9c0dc53ac8deb9550390912
Reviewed-on: https://review.openstack.org/20167
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins