HBASE-7932. Introduces Favored Nodes for region files. Adds a balancer called FavoredNodeLoadBalancer that will honor favored nodes in the process of balancing but the balance operation is currently a no-op (Devaraj Das)

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1481476 13f79535-47bb-0310-9956-ffa450edef68