Refactored Workflow with Spark
Added spark in workflow unit test
Addressed PR1 comments
Addressed comments
(CDAP-1086) Fix the Config tool only log with ERROR level, so that deprecated key warning won’t affect the dump output.
Merge pull request #836 from caskdata/feature/spark-workflow

[2.7.0] Added Spark in Workflow: CDAP-465
Merge pull request #885 from caskdata/feature/fix-config-tool-deprecate-key

(CDAP-1086) Fix the Config tool only log with ERROR level
(CDAP-1088) Added support for String type as StreamEventDecoder so that in MR and Spark it can consume stream body as String object.

Also reorganize the code in StreamInputFormat a bit to make code easier to read.
And also remove the need of Flow in the SparkKMeans test to speed up test.