Add pion information in ntuples

• Add information of the pions to the ntuples using Candidate class
• Run on the track collection after establishing the chargino candidates and compare the distance in theta/phi w/ ch1 and ch2
• For each chargino only one pion is chosen according to the distance in theta/phi
• Add vertexR, firstHitR and lastHitR to both chargino and pion in TTree

To do next:

• Investigate pion firstHitR + chargino lastHitR selection
• Check with few events if the correct true pion is found