update gui_pref class to match recent changes to sc_pref class * gui-preferences.h, gui-preferences.cc (gui_pref): Define as class with private data members. Disallow modifying data members by only providing accessor functions instead of making data members constant. Change all uses. (all_gui_preferences): New singleton class for global gui_pref data. * gui-preferences-cs.h, gui-preferences-dc.h, gui-preferences-dw.h, gui-preferences-ed.h, gui-preferences-fb.h, gui-preferences-ff.h, gui-preferences-global.h, gui-preferences-gp.h, gui-preferences-hw.h, gui-preferences-mw.h, gui-preferences-nr.h, gui-preferences-pd.h, gui-preferences-sd.h, gui-preferences-ve.h, gui-preferences-ws.h: Provide declarations but not definitions of gui_pref objects. * gui-preferences-cs.cc, gui-preferences-dc.cc, gui-preferences-dw.cc, gui-preferences-ed.cc, gui-preferences-fb.cc, gui-preferences-ff.cc, gui-preferences-global.cc, gui-preferences-gp.cc, gui-preferences-hw.cc, gui-preferences-mw.cc, gui-preferences-nr.cc, gui-preferences-pd.cc, gui-preferences-sd.cc, gui-preferences-ve.cc, gui-preferences-ws.cc: New files to provide definitions of gui_pref objects.

--- a/libgui/src/welcome-wizard.cc	Mon Jan 02 12:38:44 2023 -0500
+++ b/libgui/src/welcome-wizard.cc	Tue Jan 03 08:03:20 2023 -0500
@@ -144,7 +144,7 @@
 
     gui_settings settings;
 
-    settings.setValue (nr_allow_connection.key, m_allow_web_connect_state);
+    settings.setValue (nr_allow_connection.settings_key (), m_allow_web_connect_state);
 
     settings.sync ();
 
@@ -248,7 +248,7 @@
 
     QHBoxLayout *checkbox_layout = new QHBoxLayout;
 
-    bool allow_connection = nr_allow_connection.def.toBool ();
+    bool allow_connection = nr_allow_connection.def ().toBool ();
     if (allow_connection)
       m_checkbox->setCheckState (Qt::Checked);
     else