particle-swarm: Add a particle_speed property
particle-swarm: Enforce boundaries
particle-swarm: Add a boundary_repulsion_rate property
particle-swarm: Add a particle_distance property
particle-swarm: Add a particle_repulsion_rate property
particle-swarm: Add a particle_cohesion_rate property
particle-swarm: Add a particle_velocity_consistency property
particle-swarm: Add a FIXME note