and move the ColumnDef init into its ctor

Change-Id: I16e5252c53037663caf9f51b55adfbb7d29da549
Reviewed-on: https://gerrit.libreoffice.org/40008Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>