QETProject have is own database + add widget to edit nomenclature model

QETProject have is own ProjectDataBase, then when the database is
updated, everything that need the database is also updated trough the
signal emitted by the database.
Begin a widget to edit the NomenclatureModel

sources/qetproject.h

@@ -25,6 +25,7 @@
 #include "titleblockproperties.h"
 #include "templatescollection.h"
 #include "properties/xrefproperties.h"
+#include "projectdatabase.h"
 
 class Diagram;
 class ElementsLocation;
@@ -71,6 +72,7 @@ class QETProject : public QObject
 	
 		// methods
 	public:
+		projectDataBase *dataBase();
 		QUuid uuid() const;
 		ProjectState state() const;
 		QList<Diagram *> diagrams() const;
@@ -268,6 +270,7 @@ class QETProject : public QObject
 			   m_autosave_timer;
 		KAutoSaveFile *m_backup_file = nullptr;
 		QUuid m_uuid = QUuid::createUuid();
+		projectDataBase m_data_base;
 };
 
 Q_DECLARE_METATYPE(QETProject *)