PropertyListConfiguration no longer extends AbstractFileConfiguration.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1464156 13f79535-47bb-0310-9956-ffa450edef68
XMLPropertyListConfiguration no longer extends AbstractFileConfiguration.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1464157 13f79535-47bb-0310-9956-ffa450edef68