Laboratory for Computational Biology and Bioinformatics, EPFL (Swiss Federal Institute of Technology), EPFL-IC-LCBB, INJ 230, Station 14, CH-1014 Lausanne, Switzerland. krister.swenson@epfl.ch|Laboratory for Computational Biology and Bioinformatics, EPFL (Swiss Federal Institute of Technology), EPFL-IC-LCBB, INJ 230, Station 14, CH-1014 Lausanne, Switzerland. krister.swenson@epfl.ch