Rewritten redirection rules for new content locations

Also removed the old Dokuwiki redirects, it's been ~4 years.
The contributing redirects at the bottom won't work until the content rewrite is merged to master.
quite possible that rather than calling this trunk it will be referred to by the alias names so we might have a 4.0 and 3.2 set of docs available in an unstable state due to the SEMVER adoption.