Added a ModelSummary class to make the overview over the model content accessible via QProperty system & a SummaryWidget to show this information. Only property rowCount as a proof of concept. Other properties will follow.

libs/BeetRoundCore/model/tablemodel.h

@@ -2,6 +2,7 @@
 #define TABLEMODEL_H
 
 #include <QAbstractTableModel>
+#include "metadata.h"
 
 class QUndoStack;
 class ModelItem;
@@ -55,6 +56,12 @@ class TableModel : public QAbstractTableModel {
                    const QList<ModelItemValues>& itemValuesList,
                    const QModelIndex& parentIndex = QModelIndex());
 
+ signals:
+  void rowCountChanged();
+
+ private slots:
+  void onRowCountChanged(const QModelIndex& parent, int first, int last);
+
  private:
   /// *** members ***
   // TODO shared_ptr -> unique_ptr