[SPARK-5726] [MLLIB] Elementwise (Hadamard) Vector Product Transformer

See https://issues.apache.org/jira/browse/SPARK-5726

Author: Octavian Geagla <ogeagla@gmail.com>
Author: Joseph K. Bradley <joseph@databricks.com>

Closes #4580 from ogeagla/spark-mllib-weighting and squashes the following commits:

fac12ad [Octavian Geagla] [SPARK-5726] [MLLIB] Use new createTransformFunc.
90f7e39 [Joseph K. Bradley] small cleanups
4595165 [Octavian Geagla] [SPARK-5726] [MLLIB] Remove erroneous test case.
ded3ac6 [Octavian Geagla] [SPARK-5726] [MLLIB] Pass style checks.
37d4705 [Octavian Geagla] [SPARK-5726] [MLLIB] Incorporated feedback.
1dffeee [Octavian Geagla] [SPARK-5726] [MLLIB] Pass style checks.
e436896 [Octavian Geagla] [SPARK-5726] [MLLIB] Remove 'TF' from 'ElementwiseProductTF'
cb520e6 [Octavian Geagla] [SPARK-5726] [MLLIB] Rename HadamardProduct to ElementwiseProduct
4922722 [Octavian Geagla] [SPARK-5726] [MLLIB] Hadamard Vector Product Transformer