Experimental release for UART/BLE/Bluetooth support

This release is intended for host software development to communicate with NanoVNA using 38400 baud rate UART interface. The USB and the UART uses the same shell, so the USB interface cannot be used with this release.

Compiled with
make VERSION=v1.3.ble USE_BLE=TRUE
make gen_release VERSION=v1.3.ble

Four pins need to be connected with communication module.
GND: ground
VDD: 3.3V or 5V:5V, depends on module's voltage requirement
RXD: connect to module's TXD
TXD: connect to module's RXD

Remember to set the baud rate at 38400. To change the NanoVNA's UART baud rate, refer to SERIAL_DEFAULT_BITRATE defined in halconf.h

For UART, any USB UART module would work. For terminal software, I use "screen" in Ubuntu and "PuTTY" in Windows.

For BLE, I use HC-08 module, and tested with iOS app BLE Terminal and AirTerminal. Remember to select FFE0 for Service UUID, and FFE1 for RX/TX UUID. HC-08's speed is slow and may not be able to send all data. I also tested JDY-32, which gave miserable result.

For Bluetooth, I use HC-05 module, and tested with Bluetooth Serial Terminal app at Windows 10, and refcomm in Ubuntu. HC-05 needs carriage return and new line to complete a line. So, remember to select "Carriage Return" in "Transmit Line Ending" in the app. For refcomm in Ubuntu, please refer to
https://askubuntu.com/questions/248817/how-to-i-connect-a-raw-serial-terminal-to-a-bluetooth-connection
and follow instructions from "First step : pair the device and provide the PIN".