A. I. was funded by the FWF (Grant P20778). L. K. was funded by the NSF (Grant DMS0600800), the NSF FRG (Grant DMS-0652633), the FWF (Grant P20778) and the ERC (Grant GEMIS). V. P. was funded by the NSF FRG (Grant DMS-0854977), the NSF (Grants DMS-0854977 and DMS-0901330), by the FWF (Grants P24572-N25 and P20778), by the RFFI (Grants 11-01-00336-a, 11-01-00185-a, 12-01-33024 and 12-01-31012; Grants MK-1192.2012.1, NSh-5139.2012.1) and by the AG Laboratory GU-HSE RF (Grant ag. 11 11. G34.31.0023).