HBASE-7842 Add compaction policy that explores more storefile groups

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1465133 13f79535-47bb-0310-9956-ffa450edef68
HBASE-7842 Add missed Header

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1465162 13f79535-47bb-0310-9956-ffa450edef68