Add  note on how to generate the reference guide and where its source is kept at head of the doc
Add  note on how to generate the reference guide and where its source is kept at head of the doc

git-svn-id: 949c06ec81f1cb709fd2be51dd530a930344d7b3@1481167 13f79535-47bb-0310-9956-ffa450edef68

francisliu/hbase_namespace,francisliu/hbase_namespace,francisliu/hbase_namespace,francisliu/hbase_namespace,francisliu/hbase_namespace,francisliu/hbase_namespace,francisliu/hbase_namespace,francisliu/hbase_namespace,francisliu/hbase_namespace