actually read brightness/contrast when reading docx (bnc#875713)

It's read for the shape in oox/ , but it didn't make it any further apparently.

Change-Id: I0885a675f72d63b3d262f1ef7e42f5d2e03588b6
(cherry picked from commit 804da2a977989ba1f046847b9e00f00c83749e30)
Reviewed-on: https://gerrit.libreoffice.org/9216
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>