Allow inversion of input GPIO (#997)

* Allow inversion of input GPIO

* Fix formatting

main/ZmqttDiscovery.ino

@@ -479,7 +479,7 @@ void pubMqttDiscovery() {
 
 #  ifdef ZsensorGPIOInput
   Log.trace(F("GPIOInputDiscovery" CR));
-  char* GPIOInputsensor[8] = {"binary_sensor", "GPIOInput", "", "", jsonGpio, "HIGH", "LOW", ""};
+  char* GPIOInputsensor[8] = {"binary_sensor", "GPIOInput", "", "", jsonGpio, INPUT_GPIO_ON_VALUE, INPUT_GPIO_OFF_VALUE, ""};
   //component type,name,availability topic,device class,value template,payload on, payload off, unit of measurement
 
   Log.trace(F("CreateDiscoverySensor" CR));

main/config_GPIOInput.h

@@ -42,4 +42,7 @@ extern void GPIOInputtoMQTT();
 #  endif
 #endif
 
+#define INPUT_GPIO_ON_VALUE  "HIGH"
+#define INPUT_GPIO_OFF_VALUE "LOW"
+
 #endif