Refactor/Cleanup yarn ResourceManager for managing state via state-machines

and making most of the component interactions as asynchronous. Contributed
by Arun Murthy, Sharad Agarwal and Vinod Kumar Vavilapalli.
(Screwed up the attributions on the bunch of commits that just flew by).

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/MR-279@1153459 13f79535-47bb-0310-9956-ffa450edef68

mapreduce/CHANGES.txt

@@ -5,6 +5,10 @@ Trunk (unreleased changes)
 
     MAPREDUCE-279
     
+    Refactor/Cleanup yarn ResourceManager for managing state via
+    state-machines and making most of the component interactions as
+    asynchronous. (vinodkv, sharad and acmurthy)
+
     MAPREDUCE-2641. Fix the ExponentiallySmoothedTaskRuntimeEstimator
     and its unit test. (Josh Willis via mahadev)