New HLT2 line for DT D0->pi0pi0

D0 -> pi0 pi0 HLT2 lines where the D0 comes from B0 -> D*+ (-> D0 pi+) mu- decays. The pi+ mu- vertex is used to suppress combinatorial background. BandWidth = 1.1 MB/s This is a first attempt to see D0->pi0pi0 decays at LHCb. When running over the full sample of MinBias and applying the Hlt1 selection (TwoTrackMVA) offline no background candidates remain -> S/B ratio not clear from MC. Future studies on the ECAL deposits for the reconstruction of "merged" D0->4gamma will furher improve the efficiency of the line.

Cherry-picked from !3773 (closed)