Added Java serialization util functions back in network/common/util/JavaUtils

I was thinking that you don't expect to not have the class on hand... But sure, IllegalArgumentException because the bytes describe something invalid? The principle is to avoid RuntimeException since it is the superclass of all unchecked exceptions. If you ever wanted to catch this exception to deal with it you'd have no hope of distinguishing with a catch block. So reach for another standard and slightly more specific exception. Marginal argument here, but I think still common good practice in Java.