Update BPHY20: add BPhysBGammaFinder, modification JpsiPlus1Track for Jpsi plus e
Add BPhysBGammaFinder.h and BPhysBGammaFinder.cxx into DerivationFrameworkBPhys for reconstruction decay like Bc*->BcGamma, InDetTrackParticles are used for Gamma->e+e-. Modify JpsiPlus1Track.h and JpsiPlus1Track.cxx for using an electron as the third track. Add BPHY20BcJpsiECandidates, BPHY20ConversionCandidates in BPHY20.py