Changes made to eventually validate HITStoRDO step for BIS78 RPC.
Created new class called RPCDigitVariables (.h and .cxx) in athena/MuonSpectrometer/MuonValidation/MuonPRDTest/src based on sTGCDigitVariables class.
Added RPC hit/digit-related lines to athena/MuonSpectrometer/MuonValidation/MuonPRDTest/src/NSWPRDValAlg (.h and .cxx) to accommodate new RPCDigitVariables class.
Added RPC hit/digit-related lines to athena/MuonSpectrometer/MuonValidation/MuonPRDTest/share/NSWPRDValAlg.py to accommodate new RPCDigitVariables class.
