Extract AS to mod_cluster communication code from JBossWeb

The ClusterListener class in JBossWeb includes generally useful functionality for communicating from the JBossWeb side to the httpd side. We should re-use that code in the JBoss AS impl as well; no reason to duplicate it.

Task here is to extract the code from ClusterListener into a separate subcomponent. Package it in a separate jar so both JBossWeb and JBoss AS can both consume it without getting into dependency issues vis-a-vis each other. The JBossNative project seems like a logical place to host this code. (We can move it if not).

This should be done with an interface and extensible base implementation approach. JBoss AS will likely want to extend/alter the behavior used by standalone JBossWeb, but the ClusterListener class should be unaware of this.