UCT->GT interface

Pt asignement is handled by our code; this module reverts the GT scale change so that in the end the output is equivalent to UCT.

For taus: Assumed as GctJets for CMSSW even if they come from 2x1 clusters, only one collection (iso). Isolation switched off at 60 GeV.

Isolation recipe for EG & Taus handled by UCT2015Producer --> Some changes done here to accommodate to more recent presentations by Tom&Aaron

Added testing file to produce gt digis.