B2DsMergedPi0 and B2DsstMergedPi0 Run2 [Superseded MR!3174]

This MR superseded the previous DsMergedPi0 and DsstMergedPi0 output, see here.

Instead of using the Ds or Ds* from the current stripping lines for the resolved pi0 case, since the selected particles have already passed all the selections required to form the B with resolved pi0s, if I combine these Ds and Ds* with a merged pi0, the reconstructed B is not physical.

In this MR, I build the decay from StdLooseDsplus2KKPi and StdLooseMergedPi0, applying the same cuts used in the stripping lines Beauty2XGammaExclusiveBp2DsPi0Line and Beauty2XGammaExclusiveBp2DsstPi0Line.