Improve power saving (#1024)

* Limit tasks in loop based on voltage

* Updated disconnect voltage limit

* Fixed 8266 build

lib/HwTools/include/HwTools.h

@@ -67,7 +67,9 @@ private:
     bool ledInvert, rgbInvert;
     uint8_t vccPin, vccGnd_r, vccVcc_r;
     float vccOffset, vccMultiplier;
+    float vcc = 3.3; // Last known Vcc
     float maxVcc = 3.25; // Best to have this close to max as a start, in case Pow-U reboots and starts off with a low voltage, we dont want that to be perceived as max
+    unsigned long lastVccRead = 0;
 
     uint16_t analogRange = 1024;
     AdcConfig voltAdc, tempAdc;