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