First attempt at decode huighlighting priorities

Drag'n'drop highligting items in "Settings->Colors" to set priorities,
higher up is higher priority.  The default priorities and colours have
been changed to give a reasonable starting configuration.

Configuration.ui

@@ -2197,7 +2197,7 @@ Right click for insert and delete options.</string>
              <bool>true</bool>
             </property>
             <property name="toolTip">
-             <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Enable or disable using the check boxes and right-click an item to change the foreground color, background color, or reset the item to default values.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+             <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Enable or disable using the check boxes and right-click an item to change the foreground color, background color, or reset the item to default values. Drag and drop the items to change their priority, higher in the list is higher in priority.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
             </property>
             <property name="verticalScrollBarPolicy">
              <enum>Qt::ScrollBarAlwaysOff</enum>
@@ -3026,11 +3026,11 @@ Right click for insert and delete options.</string>
  </connections>
  <buttongroups>
   <buttongroup name="CAT_handshake_button_group"/>
-  <buttongroup name="PTT_method_button_group"/>
   <buttongroup name="split_mode_button_group"/>
   <buttongroup name="TX_mode_button_group"/>
-  <buttongroup name="CAT_stop_bits_button_group"/>
   <buttongroup name="CAT_data_bits_button_group"/>
+  <buttongroup name="PTT_method_button_group"/>
+  <buttongroup name="CAT_stop_bits_button_group"/>
   <buttongroup name="TX_audio_source_button_group"/>
  </buttongroups>
 </ui>