Backbone of getCenterPoint(...) function is complete.
As of today it only calculates the centroid but with tweeks in the
"combine" phase it will compute the centerpoint.
The full set of points is assumed to be (d+2)^k, where K is some
multiplier, so the "tree" built with the recursion is always balanced
and all terminal nodes have complete number of leaves. This also needs
to be tweaked to accept any number of points.