Convert New Style dialog to widget UI

Change-Id: Idaea69f674e1e84e3e1e649006c2d92176897fe0
Reviewed-on: https://gerrit.libreoffice.org/6607
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>