[SPARK-2429] [MLlib] Hierarchical Implementation of KMeans

I want to add a divisive hierarchical clustering algorithm implementation to MLlib. I don't support distance metrics other Euclidean distance metric yet. It would be nice to support it at other issue.
Could you review it?

Thanks!

I added the `unpersist` sentence.
https://github.com/yu-iskw/spark/commit/028d317438bdf9e3dd11246bc331f771d7d1dffe