Show firmware version number

The firmware version number is now displayed in the device list and
configuration screen headerbar.

pd-buddy-gtk.py

         self._builder.connect_signals(self)
 
         name = self._builder.get_object("name")
-        name.set_text('{} {}'.format(self.model.serport.manufacturer,
-                                     self.model.serport.product))
+        name.set_text('{} {} {}'.format(self.model.serport.manufacturer,
+                                        self.model.serport.product,
+                                        self.model.serport.serial_number))
 
         device = self._builder.get_object("device")
         device.set_text(self.model.serport.device)
         # Show the Sink page
         hst = self.builder.get_object("header-stack")
         hsink = self.builder.get_object("header-sink")
-        hsink.set_title('{} {}'.format(serport.manufacturer, serport.product))
+        hsink.set_title('{} {} {}'.format(serport.manufacturer,
+                                          serport.product,
+                                          serport.serial_number))
         hsink.set_subtitle(serport.device)
         hst.set_visible_child(hsink)