Uct2015 core

@mcepeda @isobelojalvo 

Added tau veto cut within uct producer. Introduced a variable in emulation_cfi to control the pt threshold where the veto cut is switched off. This required reconstructing some of the loops that I had previously written in order to further differentiate 4x4 vs 4x8 taus (tau veto cut cannot be applied for 4x4 taus)