Initial commit: Simple Sensor firmware for Heltec T114 with BME280

- MeshCore-based Simple Sensor firmware
- Heltec T114 without display
- BME280 sensor support (temp/humidity/pressure)
- Radio: 868.856018 MHz, SF7, BW62.5 kHz, CR4/7
- 2-byte path hash
- PlatformIO project

src/helpers/AutoDiscoverRTCClock.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <Mesh.h>
+#include <Arduino.h>
+#include <Wire.h>
+
+class AutoDiscoverRTCClock : public mesh::RTCClock {
+  mesh::RTCClock* _fallback;
+
+  bool i2c_probe(TwoWire& wire, uint8_t addr);
+public:
+  AutoDiscoverRTCClock(mesh::RTCClock& fallback) : _fallback(&fallback) { }
+
+  void begin(TwoWire& wire);
+  uint32_t getCurrentTime() override;
+  void setCurrentTime(uint32_t time) override;
+
+  void tick() override {
+    _fallback->tick();   // is typically VolatileRTCClock, which now needs tick()
+  }
+};