* added Radio::loop() virtual function

* RadioLibWrapper:  new isChannelActive() based on current RSSI being above noise_floor + THRESHOLD

src/helpers/RadioLibWrappers.h

@@ -8,11 +8,15 @@ protected:
   PhysicalLayer* _radio;
   mesh::MainBoard* _board;
   uint32_t n_recv, n_sent;
+  int16_t _noise_floor;
+  uint16_t _num_floor_samples;
+  int32_t _floor_sample_sum;
 
   void idle();
   void startRecv();
   float packetScoreInt(float snr, int sf, int packet_len);
   virtual bool isReceivingPacket() =0;
+  virtual float getCurrentRSSI() =0;
 
 public:
   RadioLibWrapper(PhysicalLayer& radio, mesh::MainBoard& board) : _radio(&radio), _board(&board) { n_recv = n_sent = 0; }
@@ -32,6 +36,8 @@ public:
     return isChannelActive();
   }
 
+  void loop() override;
+
   uint32_t getPacketsRecv() const { return n_recv; }
   uint32_t getPacketsSent() const { return n_sent; }
   void resetStats() { n_recv = n_sent = 0; }