Added setting for bill double printing.

shop/settings/shopsettingsform.cpp

@@ -45,6 +45,9 @@ ShopSettingsForm::ShopSettingsForm(QWidget *parent) :
     registerBinding(ui->decimalPlaces);
     registerBinding(ui->roundingItem);
 
+    registerBinding(ui->doublePrint);
+    registerBinding(ui->doublePrintItem);
+
     m_itemModel = new AutoTableModel<ShopItem>();
 }