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A proposal for #26 : allow customer to specify (any ?) (kernel-only ?) disks for vm creation.

A "system" or "data" disk type does not really exist (deprecated) - the kernel/cmdline attributes are the real filter here, but not implemented in this proposal.

We also lack the datacenter location for disks, that should help select the right image.
My intent is to allow user to pass any integer argument for IMAGE type - rather than populating the choices with ids, but maybe I missed something