New UDP messages to close and reconfigure WSJT-X plus more status fields

The Status(1) message acquires the new fields Frequency Tolerance, T/R
Period,  and  Configuration Name.  The  Rx  DF,  Tx DF  fields  become
unsigned (this should be a benign change which is just for correctness
as -ve values have never been possible).

The   Close(6)  message   becomes  bi-directional   allowing  external
applications to gracefully close down WSJT-X instances.

A  new  message SwitchConfiguration(14)  is  provided  that allows  an
external application to  switch the current configuration  of a WSJT-X
instance.

Another  new  message  Configure(15)  is provided  to  allow  external
applications to adjust some key parameters like the mode and submode.

See the  NetworkMessages.hpp header  commentary for full  details. The
UDPExamples/MessageAggregator reference  application has  been updated
to be able to exercise all of the above changes.

Note   that   this   commit   enforces  stricter   checking   on   the
"Settings->Reporting->Allow  UDP  requests"   option,  which  must  be
checked  before  any state  changing  incoming  messages to  a  WSJT-X
instance are processed.

UDPExamples/UDPDaemon.cpp

@@ -51,7 +51,8 @@ public:
                              , bool /*transmitting*/, bool /*decoding*/, qint32 /*rx_df*/, qint32 /*tx_df*/
                              , QString const& /*de_call*/, QString const& /*de_grid*/, QString const& /*dx_grid*/
                              , bool /* watchdog_timeout */, QString const& sub_mode, bool /*fast_mode*/
-                             , quint8 /*special_op_mode*/, QString const& /*configuration_name*/)
+                             , quint8 /*special_op_mode*/, quint32 /*frequency_tolerance*/, quint32 /*tr_period*/
+                             , QString const& /*configuration_name*/)
   {
     if (id == id_)
       {