In Print/PDF/PrintPreview border lines were missing, this
happened for merged cells. It has to do with access to the
involved Styles and/or 'Clip' set (to avoid creating everything).
Thus a 'mixed' usage of cell and merged-cell stuff was needed.
As it turns out support for this is already there, need to use
it.

Change-Id: Ic16085b97eef5c79a4501279432f43491bca350e