New JSON Interface

The behaviour of the VM is now controlled by a JSON object that is passed to the VM via control/testing in the Xen Store. It describes how to react to the next control message. Compared to the previous releases, the more aspects of the behaviour can be controlled. See the README for details.

{ "when":       "now"           // when to react
, "ack":        "ok"            // how to ack control/shutdown
, "action":     "reboot"        // how to react to control/shutdown
}