KIJIMR-141. Fixes M/R integration test running against external M/R clusters

 - System property to specify extra lib/*.jar directory to ship with M/R job.
 - System property to add jars from the current classpath.
 - Update DistributedCacheJars to understand Path.
 - Other fixes.
 - Update pom.xml to include the current project's generated jars on the classpath.