HBASE-8633 Document namespaces in HBase book (Francis Liu)

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1524153 13f79535-47bb-0310-9956-ffa450edef68
Edit of the how to make a release candidate doc.

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1524165 13f79535-47bb-0310-9956-ffa450edef68