Add a step to the installation process to verify an emergency factory will work in an emergency

[pellcorp]

So on at least one printer, plugging a USB key into the printer fails to mount the drive, which would mean in an emergency the emergency factory reset would not even work.

I am considering adding a step to the installation to get everyone to make sure they have a usb key they can use in an emergency.

[pellcorp]

For now I just added a new macro CHECK_USB_KEY, need to add to docs to verify a usb key can be used.