This work was supported in part by TIN2015-66951-C2-1-R, in part by SGR 1219, in part by CERCA Programme/Generalitat de Catalunya, and in part by the NVIDIA Corporation with the donation of the Titan Xp GPU. The work of E. Aguilar was supported by CONICYT Becas Chile. The work of B. Remeseiro was supported by the Spanish Ministry of Economy and Competitiveness under Juan de la Cierva Program (ref. FJCI-2014-21194). The work of M. Bolanos ˜ was supported by an FPU fellowship (ref. FPU15/01347). The work of P. Radeva was supported by ICREA Academia 2014.