GMEPG: Add option to zap silently between bouquets

But I now also need to allow userbouquets that are empty. Previously they
were suppressed but when not suppressed it will made silent bouquet
zapping unnessesary complicated

Ass suggeted by Firex
http://forums.openpli.org/topic/35352-graphmultiepg-m%C3%B6glich-mit-channel-updown-die-bouquets-zu-wechseln/