Simple utility class that allows chaining of {@link XMLValidator}instances. Since the class itself implements {@link XMLValidator}, multiple validators can be added by chaining these pairs; ordering of validator calls depends on ordering of the pairs.
Default semantics are quite simple: first validator of the pair is always called first, and results as/if modified by that validator are passed on to the second validator.
It is expected that this class is mostly used by actual stream reader and writer implementations; not so much by validator implementations.