MAHOUT-1493 Port Naive Bayes to Spark DSL (for comment)

Created this PR to review the patch provided by Christoph Viebig and team, Students of TU, Berlin.  It is based on Sebastian's code from before the DSL was abstracted away from Spark. 
Yeah I was having alot of trouble with the imports. I'm new to scala. I'd tried your import suggestions, but was having trouble with them.  I was getting errors when I was using:

    import RLikeDrmOps._

I put the package in:

    org.apache.mahout.classifier.naivebayes

so it is a level down from `org.apache.mahout.math` so from what I was thinking it needed the `drm.RLikeDrmOps._`