bnc#885548: Initial work on importing revisions from xlsx.

Change-Id: Ie0528490d024093cbabf38541fe70be96a9caa2e
(cherry picked from commit b92fdaa1a40bd54d279b4ac2faf19bf15468cc2f)
Reviewed-on: https://gerrit.libreoffice.org/10393
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>