Spark Integration: Streams support for Spark Jobs

Adds support to read Streams in Spark to resolve : CDAP-403

Build Running: https://builds.cask.co/browse/CDAP-DUT102-4

@anew : Please review. Thanks.
BasicSparkContext implements SparkContext which has these methods. Ideally these methods should not be called in BasicSparkContext and only be used with JavaSparkContext or ScalaSparkContext. So, its just a safe guard.