qubes/vm/qubesvm: allow looking up by UUID
qubes/vm/qubesvm: allow looking up by UUID

Also, allow lookup using VM from other app.

QubesOS/qubes-issues#866

QubesOS/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin