Nature Communications 6: Article number: 7124; DOI: 10.1038/ncomms8124 (2015); Published May 29 2015; Updated July 20 2015.
The original version of this Article contained an error in the spelling of the author W. Kockelmann, which was incorrectly given as W. Kochelmann. This has now been corrected in both the PDF and HTML versions of the Article.
