TrackedNodeModel now requires an InMemoryNodeModelSupport object.

Access to the underlying model is now indirect. This caused some adaptations in
multiple hierarchical configuration classes. Because access to the model is
now guarded by the Synchronizer the remaining failing test for
CombinedConfiguration is running now.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/branches/immutableNodes@1587026 13f79535-47bb-0310-9956-ffa450edef68
Fixed compilation failures.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/branches/immutableNodes@1587027 13f79535-47bb-0310-9956-ffa450edef68