Financial & competing interests disclosure
Our work is supported by the German Ministry for Education and Research (BMBF, grant number 0315082), the EU [FP7/2007-2013, under grant agreement n° 262055 (ESGI)], and the Max Planck Society. I thank C Weidner, D Meierhofer and A Freiwald for fruitful discussions and teamwork. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.