Core2 M5Unified independence + general fixes (#142)

- Change init sequence: I2C is now initialized before "power" init phase, to allow for I2C power control
- I2c HAL: Added read/write support for registers
- Added axp192 code from https://github.com/tuupola/axp192 to Core2 implementation
- Fixes for Core2Power
- Fix for root project CMakeLists.txt

TactilityHeadless/Source/hal/Power.h

@@ -13,7 +13,7 @@ public:
 
     enum MetricType {
         IS_CHARGING, // bool
-        CURRENT, // int32_t, mAh
+        CURRENT, // int32_t, mAh - battery current: either during charging (positive value) or discharging (negative value)
         BATTERY_VOLTAGE, // uint32_t, mV
         CHARGE_LEVEL, // uint8_t [0, 100]
     };