YARN-987. Added ApplicationHistoryManager responsible for exposing reports to all clients. Contributed by Mayank Bansal.
svn merge --ignore-ancestry -c 1556736 ../YARN-321


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1562189 13f79535-47bb-0310-9956-ffa450edef68