Support for using the Rocket Driver (com.rs.jdbc.dv.DvDriver) for a DB2 connection

[joshisa]

http://zos-spark.github.io/
http://www-03.ibm.com/systems/z/os/zos/apache-spark.html
http://www.ibm.com/support/knowledgecenter/SSLTBW_2.2.0/com.ibm.zos.v2r2.azkd100/azk_getting_started.htm

IBM z/OS platform for Spark utilizes a connection driver provided by Rocket Software to help connect to DB2 on Z data sources. I've successfully used the spark-db2 to connect with a DB2 on Linux instance running in Softlayer, however the code seems to assume use of only the DB2 JDBC driver with no override to define other DB2 drivers. A sample scala notebook can be found @ https://github.com/zos-spark/client-retention-demo/blob/master/notebooks/scala/client_retention_demo.ipynb