HBASE-9778 Add hint to ExplicitColumnTracker to avoid seeking

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.94@1576456 13f79535-47bb-0310-9956-ffa450edef68
HBASE-9778 Addendum; fix documentation markup

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.94@1576491 13f79535-47bb-0310-9956-ffa450edef68