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