Added favorite buttons to shop form.

closes #276

shop/favbutton.h

@@ -0,0 +1,22 @@
+#ifndef FAVBUTTON_H
+#define FAVBUTTON_H
+
+#include <QToolButton>
+
+class FavButton : public QToolButton
+{
+    Q_OBJECT
+
+public:
+    FavButton(QWidget *parent = 0);
+
+signals:
+    void itemDropped();
+
+    // QWidget interface
+protected:
+    virtual void dragEnterEvent(QDragEnterEvent *event) override;
+    virtual void dropEvent(QDropEvent *event) override;
+};
+
+#endif // FAVBUTTON_H