Nature Communications 7: Article number: 12621 (2016); Published: 1 September 2016; Updated: 22 November 2016

The financial support for this Article was not fully acknowledged. The Acknowledgements should have included the following:

M.B.H. and P.I. are grateful for computational resources provided by the North-German Supercomputing Alliance and the ZEDAT cluster Soroban of the Freie Universität Berlin.