closes #1: Favorite buttons has been extended with category buttons.

shop/shopform.h

@@ -42,6 +42,8 @@ private slots:
 
     void on_payButton_clicked();
 
+    void on_btnFav_clicked();
+
     void on_showPaidButton_clicked();
 
     void on_btnAddItem_clicked();
@@ -67,6 +69,9 @@ private:
 
     void loadLast();
     void loadButtons(const ShopSettingsPtr& settings);
+    void loadFavCatButtons(const QString& category);
+    void loadCatButtons();
+    void clearFavButtons();
     void fillReceiptCombo();
     void createVoucher();
     void doTempSave(bool comboChanged);