add isEMTight variable for LoosePrime WP (#261)
Add an isEMTight vairable for each photon, which could be used to define the loosePrime WP by constructing the corresponding bit mask, and then test the isEM bit against this bitmask: https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/EGammaIdentificationRun2#LoosePrime_Working_Points
Ralated to the #261 (closed)
Edited by Yixiang Zhang