Center for Biological Sequence Analysis, BioCentrum-DTU Technical University of Denmark Building 208, DK-2800 Lyngby, Denmark. hbjorn@cbs.dtu.dk|Center for Biological Sequence Analysis, BioCentrum-DTU Technical University of Denmark Building 208, DK-2800 Lyngby, Denmark. hbjorn@cbs.dtu.dk|Center for Biological Sequence Analysis, BioCentrum-DTU Technical University of Denmark Building 208, DK-2800 Lyngby, Denmark. hbjorn@cbs.dtu.dk