Some memory optimization for Arduino UNO following this thread:

https://community.openmqttgateway.com/t/arduino-uno-ethernet-shield-reboots-on-receiving-rf-signal-on-v-0-9/346/22
Rework led management to avoid use of global variables
and specify special JSON_MSG_BUFFER for arduino UNO
led can now be used for all the boards

generalize use of F macro
for memory optimization
change jsonbuffer calculation method
reduce pubsubclient max packet size for uno and nano

ZsensorGPIOInput.ino

@@ -61,7 +61,8 @@ void MeasureGPIOInput(){
     if (reading != InputState) {
       InputState = reading;
       trc(F("Creating GPIOInput buffer"));
-      StaticJsonBuffer<JSON_MSG_BUFFER> jsonBuffer;
+      const int JSON_MSG_CALC_BUFFER = JSON_OBJECT_SIZE(1);
+      StaticJsonBuffer<JSON_MSG_CALC_BUFFER> jsonBuffer;
       JsonObject& GPIOdata = jsonBuffer.createObject();
       if (InputState == HIGH) {
         trc(F("GPIO HIGH"));