YARN-954. Added the previously missed .keep file.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/YARN-321@1547654 13f79535-47bb-0310-9956-ffa450edef68
YARN-967. Added the client and CLI interfaces for obtaining ApplicationHistory data. Contributed by Mayank Bansal.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/YARN-321@1547662 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch 'apache/YARN-321' into YARN-1023
Fix some bugs and improve the tests