better handling of state dimension for single_particle_state

bfps/cpp/distributed_particles.cpp

bfps/cpp/distributed_particles.hpp

bfps/cpp/particles.cpp

bfps/cpp/particles.hpp

bfps/cpp/particles_base.cpp

bfps/cpp/particles_base.hpp

bfps/cpp/rFFTW_distributed_particles.cpp

bfps/cpp/rFFTW_distributed_particles.hpp