Add table dialog : table config can saved and loaded.

The dialog used to edit the configuration of QetGraphicsTable item can
now save and load a configuration from graphics_table.json file located
in the user config dir.

sources/ui/configsaveloaderwidget.h

@@ -42,6 +42,7 @@ class ConfigSaveLoaderWidget : public QGroupBox
 
 		QString selectedText() const;
 		QString text()const;
+		void addItem(QString text);
 
 	signals:
 		void loadClicked();