Extract core clustering infrastructure from AS cluster module

Create an ha-server-core project under projects/cluster and move the core stuff in the AS cluster module's org.jboss.ha.framework.server package to it. This includes:

1) JChannelFactory and related classes
2) ClusterPartition and related classes

The purpose of this is to:

A) Support instantiating the core services outside of the AS.
B) Allow the core services to be consumed by ha-server-cache-jbc and ha-server-cache-infinispan for use in controlling session ownership.

The AS cluster module will retain a couple subclasses of the core classes that support the @ManagementObject view.