AP_RSSI: add static create method

libraries/AP_RSSI/AP_RSSI.h

@@ -28,11 +28,16 @@ public:
         RSSI_RECEIVER           = 3
     };
 
-    // constructor
-    AP_RSSI();
+    static AP_RSSI create() { return AP_RSSI{}; }
+
+    constexpr AP_RSSI(AP_RSSI &&other) = default;
+
+    /* Do not allow copies */
+    AP_RSSI(const AP_RSSI &other) = delete;
+    AP_RSSI &operator=(const AP_RSSI&) = delete;
 
     // destructor
-    ~AP_RSSI(void);        
+    ~AP_RSSI(void);
 
     // Initialize the rssi object and prepare it for use
     void init();
@@ -52,6 +57,7 @@ public:
     static const struct AP_Param::GroupInfo var_info[];
 
 private:
+    AP_RSSI();
 
     // RSSI parameters
     AP_Int8         rssi_type;                              // Type of RSSI being used