Pion pair game

1. All particles with momentum below MAX_PION_MOMENTUM suppouse to bi
pions. Count separately positive and negative pions. Remember its index.

2. Keep events with at least one positive and one negative pion
candidate

3. For all pairs with positive and negative pions calculate recoil mass.
Keep only pairs with recoil mass in appropriate range (MIN_RECOIL_MASS,
MAX_RECOIL_MASS)

4. Keep only events with at least one good pion pairs

5. Among several pairs took one with most probable to pi pions. The
probability is calculated using ParticleID package.