Any HVM (which isn't already template-based) can be a template for
another HVM. For now do not allow simultaneous run of template and its
VM (this assumption simplify the implementation, as no root-cow.img is
needed).
Gui daemon isn't aware of multihead parameters, also gui protocol
doesn't support such information - currently by design it is configured
via Qubes RPC service.
At GUI startup send monitor layout to the VM.
