Added fade to card drag items

[REVIEW]
Added a white mask to cards that are being dragged.

Preview: http://webmup.com/1we4W/

cockatrice/src/abstractcarddragitem.cpp

@@ -3,9 +3,11 @@
 #include <QCursor>
 #include <QGraphicsSceneMouseEvent>
 #include <QDebug>
+#include <QPainter>
 
 static const float CARD_WIDTH_HALF = CARD_WIDTH / 2;
 static const float CARD_HEIGHT_HALF = CARD_HEIGHT / 2;
+const QColor GHOST_MASK = QColor(255, 255, 255, 50);
 
 AbstractCardDragItem::AbstractCardDragItem(AbstractCardItem *_item, const QPointF &_hotSpot, AbstractCardDragItem *parentDrag)
     : QGraphicsItem(), item(_item), hotSpot(_hotSpot)
@@ -40,6 +42,9 @@ AbstractCardDragItem::~AbstractCardDragItem()
 void AbstractCardDragItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
 {
     item->paint(painter, option, widget);
+
+    // adds a mask to the card so it looks like the card hasnt been placed yet
+    painter->fillRect(boundingRect(), GHOST_MASK);
 }
 
 void AbstractCardDragItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event)