Only show temp if sensor is attached. Added common functions to get temp and vcc

src/HwTools.h

@@ -0,0 +1,32 @@
+#ifndef _HWTOOLS_H
+#define _HWTOOLS_H
+
+#include "Arduino.h"
+
+#if defined(ESP8266)
+#include <ESP8266WiFi.h>
+#elif defined(ESP32)
+#include <WiFi.h>
+#endif
+
+#include <DallasTemperature.h>
+#include <OneWire.h>
+
+class HwTools {
+public:
+    static double getVcc();
+    static double getTemperature();
+
+    HwTools() {
+#if defined TEMP_SENSOR_PIN
+        oneWire = new OneWire(TEMP_SENSOR_PIN);
+        tempSensor = new DallasTemperature(this->oneWire);
+#endif
+    };
+private:
+    bool tempSensorInit, hasTempSensor;
+    OneWire *oneWire;
+    DallasTemperature *tempSensor;
+};
+
+#endif