Proximity matching should not necessarily require matching PIDs

[cpecar]

In MatchParticleProximity::Run, the following lines require that the bank-A and bank-B particles have matching PID,

      // loop over ALL bank-B particles, and find the one with the smallest proximity to
      // the current bank-A particle
      for(int row_b = 0; row_b < bank_b.getRows(); row_b++) {
        // PID must match
        if(pid_a == bank_b.getInt("pid", row_b)) {

while documentation only states that matching is done using Euclidean distance in (theta, phi). Maybe this should be changed to a check that the particle charges match.

[c-dilks]

How about a config option pid_match?

• pid_match == "strict" would require matching pid
• pid_match == "charge" requires just matching charge
• any other options we should do?