Reload schema when refreshing the browse data view

When hittin the refresh button in the Browse Data tab reload the table
schema, too, before reloading the table data. It might have changed from
outside the application as well.

See issue #496.

src/MainWindow.cpp

@@ -663,6 +663,7 @@ void MainWindow::setRecordsetLabel()
 
 void MainWindow::browseRefresh()
 {
+    db.updateSchema();
     populateTable(ui->comboBrowseTable->currentText());
 }