partial revert part of
    commit	fa135fd0
    remove unused SID constants and associated code
noticed by Julien Nabet

Also document some more of that array to make the usage more obvious

Change-Id: I4d76034df32bc85b58e4a845b246e5e28dcea49f
Reviewed-on: https://gerrit.libreoffice.org/54799Reviewed-by: Julien Nabet <serval2412@yahoo.fr>
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>