Updated Javadoc of CombinedConfiguration.

Esspecially the paragraph about thread-safety was reworked.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/branches/immutableNodes@1587028 13f79535-47bb-0310-9956-ffa450edef68
Reworked TreeUtils.

The class now dumps hierarchies of ImmutableNodes.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/branches/immutableNodes@1587029 13f79535-47bb-0310-9956-ffa450edef68