HBASE-9985 Add HBase shell command to start/stop tracing

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1542893 13f79535-47bb-0310-9956-ffa450edef68
HBASE-9985 Add HBase shell command to start/stop tracing

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1542894 13f79535-47bb-0310-9956-ffa450edef68
Add note on https://issues.apache.org/jira/browse/HBASE-8163 -- config for write-heavy situation

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1542903 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd