1. range() overloaded in SQLContext.scala
2. range() modified in python sql context.py
3. Tests added accordingly in DataFrameSuite.scala and python sql tests.py

Author: animesh <animesh@apache.spark>

Closes #6609 from animeshbaranawal/SPARK-7980 and squashes the following commits:

935899c [animesh] SPARK-7980:python+scala changes