Star Simulator updates

Fixed a number of issues.  One resolving properly (albeit a more minor issue) position - Center of Mass vector so that distance to the radial center of a given celestial object is computed properly in the spherical coordinate direction of position - center of mass.  Secondly, issue regarding instantaneous velocity resolved (improperly computing this from the unit vector of position - center of mass position), so that this is now computed from the properly length scale.  Thirdly, in computing big M for instantaneous velocity, instead computing for the all given celestial masses whose radial magnitude is such that r_s > r where r is the distance of any star less than a given star s.

Updates finished.

At initialization portion of code, you can change the distribution of mass along the z axis by changing a numeric divisor where approaching 1 means that a given distribution is expressed by the original z axis parametric random distribution given.  You might notice, that changing this value, with greater mass distribution of stars outside of  a quasi 2 dimensional rotational plane, and having added stars into a given system, tends to lead to a non zero momentum  barycentric system.  While those systems tending towards flattened rotational galactic planes to be more stable.  As opposed to a system that has no initial linear momentum, also it would be noticed that the frequency of stars gobbling other stars is less so.