Computational Biology, Department of Physics and Measurement Technology, Linköping University, Linköping, Sweden. jmp@ifm.liu.se|Computational Biology, Department of Physics and Measurement Technology, Linköping University, Linköping, Sweden. jmp@ifm.liu.se|Computational Biology, Department of Physics and Measurement Technology, Linköping University, Linköping, Sweden. jmp@ifm.liu.se