OOZIE-1460 Implement and Document security for HA (rkanter)

git-svn-id: https://svn.apache.org/repos/asf/oozie/trunk@1531170 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk
Merge remote branch 'origin/trunk' into trunk-gd