Default fan speed should be stored in EEPROM

[ryan-summers]

The default fan speed should be saved somewhere. It's currently only stored via MQTT, but this feature may be desired for MQTT-less implementations.

[ryan-summers]

@jordens With the addition of fan speed stored in EEPROM and removal of gateway/ip/netmask, I was curious to hear your opinions on maintaining backward compatibility of settings with the NGFW.

Two main questions:

• Do we want to "auto-upgrade" the settings when necessary (e.g. populate a default fan-speed) without throwing away previous configurations?
• Do we want to ensure that settings remain in place such that if the user reverts to an older Booster release, the EEPROM settings will remain usable?

[jordens]

I would say yes to both. Unless there are problems like storage space.