Add model and serial numbers

[austinmroczek]

Retain the appliance model number and serial number when loading location info. I used dict.get() in case other appliances don't provide these values.

This could later be added to Home Assistant for a more complete DeviceInfo.

I didn't add specific tests, but existing tests pass.

[abmantis]

Thanks! Please update the branch with master, since it fixes the lint

[austinmroczek]

updated, thanks