returns an n×n matrix A in
which A[[i,j]]=1 if the cells in the bounded cell Voronoi diagram
corresponding to the ith and jth cell in the list are touching and 0 if not.
The matrix that is returned is symmetric.
The input gives a list of points
specifying the cell nuclei.
If the pruned Delaunay triangulation is already
known it is more efficient to use delaunayTriangulationToConnectionMatrix
instead of pointsToConnectionMatrix.