support. Can even create multiple jailed nodes on the same physical
node. Sorry, no sharing of physical nodes yet (between slices).
Also no link support yet; coming later.

The syntax is an extension of the current hack syntax:

        " <node uuid=\"" + node_uuid + "\" " +\
        "       nickname=\"geni1\" "+\
        "       phys_nickname=\"geni1\" "+\
        "       virtualization_type=\"emulab-vnode\" " +\
        "       virtualization_subtype=\"emulab-jail\"> " +\
        " </node>"

This only works on sites that already can do jails.