YARN-1001. Added a web-service to get statistics about per application-type per state for consumption by downstream projects. Contributed by Zhijie Shen.
svn merge --ignore-ancestry -c 1523855 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1523856 13f79535-47bb-0310-9956-ffa450edef68