Huge setup fix, compilation fixes, auto brightness fix

Includes a huge setup fix.

but also auto-brightness scale is fixed (resolution was wrong, so it was 0=0% 1=50% 2=100% 3=0% 4=50% 5=100% (basically two times the scale). Also, auto-brightness is now round to nearest instead of down

Updated libraries: Button, WiFiManager

Fixed compilation error (wrong variable name used)

Fixed debug serial format, so it compiles again with debugging on