HIVE-4812 : Logical explain plan (Gunther Hagleitner V via Navis)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1501036 13f79535-47bb-0310-9956-ffa450edef68
HIVE-4796 : Increase coverage of package org.apache.hadoop.hive.common.metrics (Ivan Veselovsky)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1501052 13f79535-47bb-0310-9956-ffa450edef68
HIVE-4580 : Change DDLTask to report errors using canonical error messages rather than http status codes (Eugene Koifman via Ashutosh Chauhan)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1501053 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HIVE-4791-trunk-gd