[Sprint:37] XD-1791 Add Spark job

 - Add `SparkTasklet` that can run spark application in `client` mode
     - In client mode, the spark job gets executed within container as a job module
 - Add module options to provide
     - master: to point to spark master
     - mainClass: the main class for the spark application
     - appJar: the bundled jar for the application and its dependencies
     - programArgs: the comma separated program arguments for the main class
@mminella we are adding a Spark Tasklet to Spring Hadoop, it's just not ready yet. So, XD moves a bit faster and we'll synch things up at a later point.