sixtracklib/common: Add API to NS(ParticleS) to allow easier access to individual NS(Particles) objects by their index
sixtracklib/common: Add API to NS(ParticleS) to allow easier access to individual NS(Particles) objects by their index

SixTrack/SixTrackLib,SixTrack/SixTrackLib,SixTrack/SixTrackLib,SixTrack/SixTrackLib