Unmanaged machines

[bluecmd]

We should support unmanaged / self-reported machines - as in an operator takes a USB stick or something and boots some machine somewhere into Tateru.

Tateru Installer would then sit there and try to do the installer-callback until an installation order has been received. We can use that to populate our machines database with serial number, asset tag, etc. and do an inventory lookup like we would do for bare metal machines.

This would make it easy to use for things like Raspberry Pi, workstations, etc. that might require some smart hands to do the boot sequence.