[SPARK-2199][mllib]

"created by ..." comments generated by intellij are removed
[SPARK-2199][mllib]

imports organized
[SPARK-2199][mllib]

imports are organized and "created by..." comments are removed
[SPARK-2199][mllib]

docs added
[SPARK-2199][mllib]

code style fixed
[SPARK-2199][mllib]

a pair of classes are private now