Removing (nearly) all code from INO files

[timmbogner]

I've been meaning to do this for a long time. Having code in multiple places was a headache for development and doesn't make sense any longer.

The gateway.ino now looks like this:

#include "fdrs_gateway_config.h"
#include <fdrs_functions.h>

void setup() {
beginFDRS();
}

void loop() {
loopFDRS();
}

So fresh and so clean, clean!

I don't think this should change much in execution, but I've been surprised before. I'm keeping it in this PR until I've finished testing.