Switch to runtime configuration instead of compile time

[DavyLandman]

As suggested by @gertziel and @Frankvd81 it would be nice to configure the Kiwi after flashing the firmware.

Steps:

• put button on back of the kiwi to trigger "maintenance mode" that starts an access point and allows a user to upload a config file
• store config file in file system part of the memory
• replace most compile-time defines into runtime defines
• plot lacking wifi connectivity on screen
• release binaries using github actions