priv impl and scaffold for driver

bbnow_driver.cpp

@@ -0,0 +1,20 @@
+#include "bbnow_driver.hpp"
+
+esp_err_t BBNowDriver::init()
+{
+    return ESP_OK;
+}
+
+esp_err_t BBNowDriver::deinit()
+{
+    return ESP_OK;
+}
+
+esp_err_t BBNowDriver::send(
+    const MacAddress& destination,
+    const uint8_t* data,
+    size_t size
+)
+{
+    return ESP_OK;
+}