Reduce visibility of some classes in the org.modeshape.jcr package

Several public classes in the org.modeshape.jcr package [1] are not used outside of the package and are more of an implementation detail that users should have no need, and I think they should not be public. Examples include:

• CndNodeTypeSource
• CorrespondenceId
• NodeDefinitionId
• PropertyDefinitionId

[1] http://docs.jboss.org/modeshape/1.0.0.Beta1/api/org/modeshape/jcr/package-summary.html