ResteasyViolationException obscures cause if there is one

If an exception occurs in a validator, a ResteasyViolationException is created with its exception field set to the exception. This means that if you want to log a stack trace of the problem, you need to have the RestEasy API on your classpath so you can cast the ConstraintValidationException to the actual type and access the relevant field. It would be nice if the RVE also set the exception as its cause, so that the cause can be retrieved using the standard Throwable#getCause() method.