when clicking a transaction on the overview page, send the user to the transactions page

src/qt/overviewpage.h

@@ -3,6 +3,10 @@
 
 #include <QWidget>
 
+QT_BEGIN_NAMESPACE
+class QModelIndex;
+QT_END_NAMESPACE
+
 namespace Ui {
     class OverviewPage;
 }
@@ -23,6 +27,9 @@ public slots:
     void setBalance(qint64 balance, qint64 unconfirmedBalance);
     void setNumTransactions(int count);
 
+signals:
+    void transactionClicked(const QModelIndex &index);
+
 private:
     Ui::OverviewPage *ui;
     WalletModel *model;