Cleanup general definitions in MQUnifiedSensor.h

ADC_RESOLUTION is unused, and retries and retry_interval are only used by getVoltage().
Thus, remove ADC_RESOLUTION and move retries and retry_interval to MQUnifiedsensor.cpp.
Furthermore, these three definitions have generic names so it's easy to have them
conflict with a user's sketch that imports MQUnifiedSensor.h.

src/MQUnifiedsensor.cpp

@@ -1,5 +1,8 @@
 #include "MQUnifiedsensor.h"
 
+#define retries 2
+#define retry_interval 20
+
 MQUnifiedsensor::MQUnifiedsensor(String Placa, float Voltage_Resolution, int ADC_Bit_Resolution, int pin, String type) {
   this->_pin = pin;
   Placa.toCharArray(this->_placa, 20);

src/MQUnifiedsensor.h

@@ -6,10 +6,6 @@
 
 /***********************Software Related Macros************************************/
 
-#define ADC_RESOLUTION 10 // for 10bit analog to digital converter.
-#define retries 2
-#define retry_interval 20
-
 class MQUnifiedsensor
 {
   public: