MSWord has a page-style vertical alignment (center/bottom/justify)
setting that was lost after round-tripping through LibreOffice.

Writer does not currently have the ability to vertically align text
outside of a frame, but the setting should be preserved for
interoperability.

Change-Id: I91ae841b91ca2f2dd1b68212fdcdf830c7cef22a
Reviewed-on: https://gerrit.libreoffice.org/18480Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Justin Luth <justin_luth@sil.org>