Update handling of NoClassDefFoundError by the RepositoryClassLoader

The RepositoryClassLoader wraps any exception other than a ClassNotFoundException that occurs during class loading in a ClassNotFoundException with a message that includes the load exception message. This does not show the cause correctly even with j2se1.4+ due to some legacy ClassNotFoundException behavior. Since NoClassDefFoundError are difficult to debug without the actual cause this should be broken out as simply rethrown.