consider golden spiral in RegionSearchClusterData

[cchris28]

Consider the golden spiral method to generate a list of evenly distributed points on a unit disk. Then select a random subset to use as cluster offsets in RegionSearchClusterData instead of the random angular offsets currently used. This has the advantage of closer to even distribution around the cluster pointing at any part of the sphere for small angular radius. For larger angular radius the distribution is denser near the cluster. Probably this could be fixed. But the link below gives easily adapted python.

https://stackoverflow.com/questions/9600801/evenly-distributing-n-points-on-a-sphere/44164075#44164075

The spiral generation code example:

from numpy import pi, cos, sin, sqrt, arange
import matplotlib.pyplot as pp

num_pts = 100
indices = arange(0, num_pts, dtype=float) + 0.5

r = sqrt(indices/num_pts)
theta = pi * (1 + 5**0.5) * indices

pp.scatter(rcos(theta), rsin(theta))
pp.show()