Added new listener interface for FileHandler.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1462193 13f79535-47bb-0310-9956-ffa450edef68
Added adapter class for FileHandlerListener.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1462194 13f79535-47bb-0310-9956-ffa450edef68