MAHOUT-1464

MAHOUT-1464 looks ready to me but can't push it yet.

My build is broken from an unrelated mr-legacy test so I'll wait to push it until my local build passes but wanted to get this out for review if anyone cares.

I took out the epinions and movielens examples, will add them back in with the CLI driver maybe. 
colCounts or whatever we call it is just as efficient, is distributed and tells the reader what is the important value.