also some improvements to the plugin

Change-Id: I0e3a519d70756e577fcb1bd47dd66864b5b4c871
Reviewed-on: https://gerrit.libreoffice.org/23289Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>