Department of Computer Science and Genome Center, University of California, Davis, CA 95616, USA. koehl@cs.ucdavis.edu|Department of Computer Science and Genome Center, University of California, Davis, CA 95616, USA. koehl@cs.ucdavis.edu|Department of Computer Science and Genome Center, University of California, Davis, CA 95616, USA. koehl@cs.ucdavis.edu|Department of Computer Science and Genome Center, University of California, Davis, CA 95616, USA. koehl@cs.ucdavis.edu|Department of Computer Science and Genome Center, University of California, Davis, CA 95616, USA. koehl@cs.ucdavis.edu