[vtkusers] New Example: KMeans Clustering

[David Doria]

This is a useful functionality that is quite buried in VTK. This
example demonstrates how to cluster 3D points using the KMeans
algorithm.

http://www.vtk.org/Wiki/VTK/Examples/KMeansClustering

I thought it might be useful for some people to see that it is available.

Thanks,

David