Spark now uses configure style

- Spark uses configurer style API : CDAP-382

Build running here: https://builds.cask.co/browse/CDAP-DUT316-2

This opens two more related (but independent to this merge) issues: 
CDAP-989: Doc changes for the Spark configurer style API
CDAP-990: Apps and Guide changes to use Spark configurer style API
You have to move this class to cdap-api. Replace the one in `cdap-api/src/main/java/co/cask/cdap/api/spark/SparkSpecification.java`