closing #72, this issue will be part of #47 when introducing reference particles a la OPAL-t

src/Classic/Algorithms/PartBunch.cpp

@@ -1921,6 +1921,8 @@ void PartBunch::calcMoments() {
     }
 
     /*
+      Issue #72 is touching on this
+
       In OPAL Cycl the particle with ID=0
       is a special particle, a kind of design particle.