ParticleMask: using helper::set that can be easily printed
ParticleMask: using helper::set that can be easily printed

Former-commit-id: 8304d08c7d38ee3858eaae9ff65fec06afc755f5
Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,hdeling/sofa,hdeling/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,Anatoscope/sofa,hdeling/sofa,hdeling/sofa,Anatoscope/sofa