European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, D-69117, Germany. charles.girardot@embl.de.|European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, D-69117, Germany.|European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, D-69117, Germany.|European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, D-69117, Germany.|European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, D-69117, Germany.