Allow desktop switching between xen instances with freenx sessions

Once Xen is integrated into the/an ubuntu kernel, there should be an easy way of switching contexts. The usual method is a set of virtual network interfaces, so ssh can be used to access each xenU instance. This is fine for servers which are typically stripped down, but there are valid use cases for having desktop sessions: nx / freenx could provide this by allowing connection to these xen instances from the host and other machines.