message: core: add comments for constexprs
diff: @@ -23,10 +23,15 @@ class System;
  class DroneCore
  {
  public:
  + /** @brief Default UDP bind IP (accepts any incoming connections). */
  static constexpr auto DEFAULT_UDP_BIND_IP = "0.0.0.0";
  + /** @brief Default UDP bind port (same port as used by MAVROS). */
  static constexpr int DEFAULT_UDP_PORT = 14540;
  + /** @brief Default TCP remote IP (localhost). */
  static constexpr auto DEFAULT_TCP_REMOTE_IP = "127.0.0.1";
  + /**< @brief Default TCP remote port. */
  static constexpr int DEFAULT_TCP_REMOTE_PORT = 5760;
  + /**< @brief Default serial baudrate. */
  static constexpr int DEFAULT_SERIAL_BAUDRATE = 57600;
  /**
  