Just a skeleton, doesn't use comphelper::OStorageHelper yet.

Change-Id: Ic83e05b3a041c0c572e294eacd5b9dcb6eeae897
Reviewed-on: https://gerrit.libreoffice.org/40703Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>