External hypervisor VMs integration

Added v2v module - added ability to list VMs from external source
(non KVM) via libvirt.

The v2v module aims to add the ability to vdsm to integrate with
external hypervisors and import VMs directly to storage domain.
It will have an API for listing VMs with basic properties (such as name,
disks and network) as well as an API for importing an actual VM from
external hypervisor.

v2v module will use virt-v2v to convert the VM from other hypervisors as
well as libvirt for listing existing VMs.

Change-Id: I7dcfb860626a844d1d08590274b508519a33f4a3
Signed-off-by: Shahar Havivi <shaharh@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/33309
Tested-by: Shahar Havivi <shavivi@redhat.com>
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>