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)

Please use another label for this, maybe you can rename them to relativeJetIsolationForElectronsCut, relativeJetIsolationForTausCut  and relativeJetIsolationForTausLimit ?