Add isBlank and isNotBlank to Strings.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1617193 13f79535-47bb-0310-9956-ffa450edef68
Fix typo.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1617194 13f79535-47bb-0310-9956-ffa450edef68
Use parametrized logging.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1617198 13f79535-47bb-0310-9956-ffa450edef68