Partly supported by the spanish grant MINECO-13-FPA2012-35043-C02-02. In addition, they acknowledge financial support from the Ramon y Cajal grant RYC-2011-07593 as well as the EU CIG grant UE-14-GT5LD2013-618459. The work of A.P is funded by the Asturian government’s SEVERO OCHOA grant BP14-003. The work of J.S. is funded by the Asturian government’s CLARIN grant ACB14-27.