Refactor Wi-Fi log download

Use MAVLink LOG_REQUEST_DATA and LOG_DATA for download log instead of console.
Make Wi-Fi download default way of downloading the log.
Make `log` command only print the header and `log dump` dump the log.

gazebo/flix.h

@@ -45,7 +45,8 @@ void normalizeRC();
 void calibrateRC();
 void calibrateRCChannel(float *channel, uint16_t zero[16], uint16_t max[16], const char *str);
 void printRCCalibration();
-void dumpLog();
+void printLogHeader();
+void printLogData();
 void processMavlink();
 void sendMavlink();
 void sendMessage(const void *msg);