add ID_PATH and DEVNAME as fallbacks for the camera id

[NiklasNeugebauer]

This resolves #69

[falkoschindler]

I wonder if we should always use the ID_VENDOR_ID and ID_MODEL_ID, like

parts = [
    device.get('ID_VENDOR_ID'),
    device.get('ID_MODEL_ID'),
    device.get('ID_SERIAL_SHORT') or device.get('ID_PATH') or device.get('DEVNAME'),
]
return '-'.join(parts) if all(parts) or None

🤔

[NiklasNeugebauer]

Added. We might run into the case of these also not being available while just the devpath realistically must be, but lets see if that ever happens

[NiklasNeugebauer]

Actually, I added the final "only devname" case