HDFS-6278. Create HTML5-based UI for SNN. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1589613 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6279. Create new index page for JN / DN. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1589618 13f79535-47bb-0310-9956-ffa450edef68