Add remote fn to turn on/off debug serial output #143
Description
It may be useful to not have to recompile the entire project in order to turn on/off serial debugging.
Particle provides a means of defining functions in the firmware which can be called from the Particle dashboard. This seems like the best way to turn on/off serial debugging without having to recompile.
One way of implementing this would be to add serial debug functions which branch on some globally defined bool. The bool would be set via particle cloud functions. All serial debug macros are defined in src/settings.h