[LOG4J2-508] Add new Levels: NOTICE, DIAG, VERBOSE. VETO by Remko Popma. Reverse-merging r1560602 through r1560601. 

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1561090 13f79535-47bb-0310-9956-ffa450edef68
[LOG4J2-508] Add new Levels: NOTICE, DIAG, VERBOSE. VETO by Remko Popma. Reverse-merging r1560356 through r1560355.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1561091 13f79535-47bb-0310-9956-ffa450edef68