TEZ-56. Remove MR references rom DAG, Vertex, Task, TaskAttempt. (sseth)


git-svn-id: https://svn.apache.org/repos/asf/incubator/tez/branches/TEZ-1@1470655 13f79535-47bb-0310-9956-ffa450edef68
TEZ-57. Remove MR references from AMNode. (sseth)


git-svn-id: https://svn.apache.org/repos/asf/incubator/tez/branches/TEZ-1@1470656 13f79535-47bb-0310-9956-ffa450edef68