Show UnsavedDocumentsDialog when closing window or quitting application

so user can save and or discard docs more efficiently.

pglab/MasterController.h

@@ -7,6 +7,7 @@
 #include <map>
 #include <memory>
 #include "sqlite/SQLiteConnection.h"
+#include "querytool/SqlDocumentRegistry.h"
 
 
 class ConnectionController;
@@ -24,6 +25,10 @@ public:
 
 	ConnectionController* connectionController();
     SQLiteConnection& userConfigDatabase();
+
+    SqlDocumentRegistry& sqlDocumentRegistry() { return m_sqlDocumentRegistry; }
+    /// Asks once about all modified documents of all windows. Returns false when quitting must be aborted.
+    bool confirmQuit(QWidget *parent);
     
 signals:
 
@@ -31,6 +36,7 @@ public slots:
 
 private:
     SQLiteConnection m_userConfigDatabase;
+    SqlDocumentRegistry m_sqlDocumentRegistry;
 	ConnectionController* m_connectionController = nullptr;
 };