JGRP-1859 Allow Configurator to load protocols from a specific classloader

https://issues.jboss.org/browse/JGRP-1859

The end goal is to allow custom protocols in WildFly via:
<protocol type="org.foo.Bar" module="org.foo"/>

where module defines the module from which to load the protocol class.  Currently, JGroups lacks the ability to do this from the Configurator - which WildFly currently uses to configure the protocol stack.