This publication is based in part upon work supported by Grant No. KUK-C1-013-04, made by (KAUST), and by the U.S. NSF under Grant No. DMS-0907773 (B. D.). A. G. acknowledges support from a Reintegration Grant under EC Framework VII. The work of J. H. M. was supported by the Swiss National Science Foundation under Grants No. 200021-126666/1&2 and No. 200020-143613.