Invalid @SuppressWarnings syntax

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1616045 13f79535-47bb-0310-9956-ffa450edef68
Use non-deprecated Assert class

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1616047 13f79535-47bb-0310-9956-ffa450edef68
Use Level.XXXX rather than deprecated Priority.XXXX

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1616048 13f79535-47bb-0310-9956-ffa450edef68