It is useful to generate linear data for easy testing of linear models and in general. Scala already has it. This is just a wrapper around the Scala code.

Author: MechCoder <manojkumarsivaraj334@gmail.com>

Closes #6715 from MechCoder/generate_linear_input and squashes the following commits:

6182884 [MechCoder] Minor changes
8bda047 [MechCoder] Minor style fixes
0f1053c [MechCoder] [SPARK-8265] Add LinearDataGenerator to pyspark.mllib.utils