Support distributed cache files and archives on spark on yarn and attempt to cleanup the staging directory on exit
Adding in the --addJars option to make SparkContext.addJar work on yarn and cleanup
the classpaths
Merge remote-tracking branch 'tgravescs/sparkYarnDistCache'

Closes #11

Conflicts:
	docs/running-on-yarn.md
	yarn/src/main/scala/org/apache/spark/deploy/yarn/ClientArguments.scala