Created a runner_doself2_force_vec function. Multiple variations,...

Created a runner_doself2_force_vec function. Multiple variations, runner_doself2_force_vec vectorises straight from the serial. runner_doself2_force_vec_2 vectorises by caching properties needed in the interaction. runner_doself2_force_vec_3 builds on runner_doself2_force_vec_2 and stores the interactions in a secondary cache and performs interaction after looping over all possible pj particles.