Added ability to change time format string for when you're in System

Clock mode. Fixed code so that editing settings in the settings dialog
will now immediately take effect in the program.

mainsettingsdialog.h

@@ -16,6 +16,9 @@ public:
     explicit MainSettingsDialog(QWidget *parent = 0);
     ~MainSettingsDialog();
 
+signals:
+    void updatedSettings();
+
 private slots:
     void updateSettings();