Configuration interface now extends SynchronizerSupport.

Implementations of the interface methods are provided by AbstractConfiguration.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1481151 13f79535-47bb-0310-9956-ffa450edef68
Do not call non-private, non-final method from constructor.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/trunk@1481152 13f79535-47bb-0310-9956-ffa450edef68