AI-deck individual and different passwords

[tobbeanton]

For some users a separate passwords for each AI deck is needed for security reasons. Adding the password in the .config of the STM firmware is not great in that case - it would be much better to store it in flash/EEPROM on the AIdeck itself, to allow swapping the deck to a different drone.

In summary: add a possibility to have WiFi-credentials saved in each AI-deck