Add ghost probability filtering and tighten soft pion selection in CharmHad

This MR adds two things:

• Filtering on the track ghost probability (TRGHOSTPROB) for all basic charged inputs to CharmHad; and
• A tightening of the common soft pion selection in CharmHad.

The former enables the latter. We've decided to do the latter because it reduces the background significantly for an almost negligible loss of signal.

The exact soft pion selection could be tuned further, but the implementation here (PT > 200*MeV and TRGHOSTPROB < 0.15) is seen as a 'safe' option that already helps a lot.

/cc @adicanto @acontu @spradlin @mrwillia