Improvements in B -> (X) tau l lines

• Fix bug in units for eta' (electron energy threshold from 400 GeV -> 350 MeV)
• Renamed file b_to_xtaul_hlt2 -> b_to_xtaul_3pi_hlt2
• Renamed file b_to_tautau_hlt2 -> b_to_taul_3pi_hlt2
• Renamed lines 'Hlt2RD_BsToTauMu_TauTo3Pi_OS' and 'Hlt2RD_BsToTauE_TauTo3Pi_OS' to 'Hlt2RD_BdToTauMu_TauTo3Pi_OS' and 'Hlt2RD_BdToTauE_TauTo3Pi_OS'. These lines were moved from the file b_to_ll_LFV_hlt2.py to b_to_taul_3pi_hlt2. Prescaling was removed.
• Selections for electrons, muons and tauons are shared
• Selections for B(s) modified to align b_to_taul lines.
• tau vertex chi2 selection loosened from 6 -> 9
• Introduced soft cuts on tau_bpvvdrho range

Selections summary.