message: Only calculate shape rect when it has been changed
  Previously, calculateRect() was called each time the boundingRect of the item was requested. This is extremely inefficient.
  The rect is now only calculated when the item has been edited.
diff: @@ -19,12 +19,16 @@ class Shape : public QGraphicsItem {
  QWidget* widget);
  void addInput(QString input);
  void addInput(QStringList input);
  - void addOutput(QString output) { m_outputs.append(output); }
  - void addOutput(QStringList output) { m_outputs.append(output); }
  - void setName(QString name) { m_name = name; }
  + void addOutput(QString output);
  + void addOutput(QStringList output);
  + void setName(QString name);
  private:
  - QRectF calculateRect() const;
  + void calculateRect();
  + QRectF m_rect;
  + bool m_hasChanged = true; // Flag is set whenever the item has changed (ie.
  + // when new descriptors have been added)
  +
  QPainterPath drawALUPath(QRectF boundingRect) const;
  ShapeType m_type;
  @@ -41,6 +45,11 @@ class Shape : public QGraphicsItem {
  QList<QPointF> m_inputPoints;
  QList<QPointF> m_outputPoints;
  + // Top- and bottom center-points of the shape
  + // Can be used to affix labels to shapes in the graphics scene
  + QPointF m_topPoint;
  + QPointF m_bottomPoint;
  +
  // drawing constants
  qreal nodeHeight = 20;
  qreal nameFontSize = 10;
  