Added the ability for GVRET serial to try both normal mode and ESP32 mode.

This way it basically automatically detects the proper connection type to use
and uses that mode to connect. That allows both types to work transparent
to the user. They select GVRET and the serial port and away they go.

connections/gvretserial.h

@@ -84,6 +84,7 @@ protected:
     bool isAutoRestart;
     bool continuousTimeSync;
     bool useTcp;
+    bool espSerialMode; //special serial mode for ESP32 based boards - no flow control and much slower serial baud speed
     QSerialPort *serial;
     QTcpSocket *tcpClient;
     QUdpSocket *udpClient;