[SPARK-4596][MLLib] Refactorize Normalizer to make code cleaner

In this refactoring, the performance will be slightly increased due to removing 
the overhead from breeze vector. The bottleneck is still in breeze norm 
which is implemented by activeIterator. 

This inefficiency of breeze norm will be addressed in next PR. At least, 
this PR makes the code more consistent in the codebase.