save/load QetGraphicsTableItem to/from .qet file

sources/qetgraphicsitem/ViewItem/nomenclaturemodel.h

@@ -1,4 +1,4 @@
-/*
+/*
         Copyright 2006-2020 QElectroTech Team
         This file is part of QElectroTech.
 
@@ -20,6 +20,7 @@
 
 #include <QAbstractTableModel>
 #include <QPointer>
+#include <QDomElement>
 
 class QETProject;
 
@@ -45,6 +46,10 @@ class NomenclatureModel : public QAbstractTableModel
 		QETProject *project() const;
 		void autoHeaders();
 
+		QDomElement toXml(QDomDocument &document) const;
+		void fromXml(const QDomElement &element);
+		static QString xmlTagName() {return QString("nomenclature_model");}
+
 	private:
 		void dataBaseUpdated();