[SPARK-7015] [MLLIB] [WIP] Multiclass to Binary Reduction: One Against All

initial cut of one against all. test code is a scaffolding , not fully implemented.
This WIP is to gather early feedback.

Author: Ram Sriharsha <rsriharsha@hw11853.local>

Closes #5830 from harsha2010/reduction and squashes the following commits:

5f4b495 [Ram Sriharsha] Fix Test
386e98b [Ram Sriharsha] Style fix
49b4a17 [Ram Sriharsha] Simplify the test
02279cc [Ram Sriharsha] Output Label Metadata in Prediction Col
bc78032 [Ram Sriharsha] Code Review Updates
8ce4845 [Ram Sriharsha] Merge with Master
2a807be [Ram Sriharsha] Merge branch 'master' into reduction
e21bfcc [Ram Sriharsha] Style Fix
5614f23 [Ram Sriharsha] Style Fix
c75583a [Ram Sriharsha] Cleanup
7a5f136 [Ram Sriharsha] Fix TODOs
804826b [Ram Sriharsha] Merge with Master
1448a5f [Ram Sriharsha] Style Fix
6e47807 [Ram Sriharsha] Style Fix
d63e46b [Ram Sriharsha] Incorporate Code Review Feedback
ced68b5 [Ram Sriharsha] Refactor OneVsAll to implement Predictor
78fa82a [Ram Sriharsha] extra line
0dfa1fb [Ram Sriharsha] Fix inexhaustive match cases that may arise from UnresolvedAttribute
a59a4f4 [Ram Sriharsha] @Experimental
4167234 [Ram Sriharsha] Merge branch 'master' into reduction
868a4fd [Ram Sriharsha] @Experimental
041d905 [Ram Sriharsha] Code Review Fixes
df188d8 [Ram Sriharsha] Style fix
612ec48 [Ram Sriharsha] Style Fix
6ef43d3 [Ram Sriharsha] Prefer Unresolved Attribute to Option: Java APIs are cleaner
6bf6bff [Ram Sriharsha] Update OneHotEncoder to new API
e29cb89 [Ram Sriharsha] Merge branch 'master' into reduction
1c7fa44 [Ram Sriharsha] Fix Tests
ca83672 [Ram Sriharsha] Incorporate Code Review Feedback + Rename to OneVsRestClassifier
221beeed [Ram Sriharsha] Upgrade to use Copy method for cloning Base Classifiers
26f1ddb [Ram Sriharsha] Merge with SPARK-5956 API changes
9738744 [Ram Sriharsha] Merge branch 'master' into reduction
1a3e375 [Ram Sriharsha] More efficient Implementation: Use withColumn to generate label column dynamically
32e0189 [Ram Sriharsha] Restrict reduction to Margin Based Classifiers
ff272da [Ram Sriharsha] Style fix
28771f5 [Ram Sriharsha] Add Tests for Multiclass to Binary Reduction
b60f874 [Ram Sriharsha] Fix Style issues in Test
3191cdf [Ram Sriharsha] Remove this test, accidental commit
23f056c [Ram Sriharsha] Fix Headers for test
1b5e929 [Ram Sriharsha] Fix Style issues and add Header
8752863 [Ram Sriharsha] [SPARK-7015][MLLib][WIP] Multiclass to Binary Reduction: One Against All