YARN-717. Put object creation factories for Token in the class itself and remove useless derivations for specific tokens. Contributed by Jian He.
MAPREDUCE-5289. Updated MR App to use Token directly after YARN-717. Contributed by Jian He.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1488616 13f79535-47bb-0310-9956-ffa450edef68