Bug 150347 Support binary stream as preview image.
See 144843. We need model to save binary strame as report preview image. Currently, preview image is an external image. Maybe need a type to distinguish preview image type.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/activity/NotificationEvent.java
protected DesignElement target = null;
	/**
	 * The sender of the event. This is generally the UI that made the change.
	 * This allows the UI to ignore, if it chooses, events that indicate changes
	 * that the that UI made itself.
	 */
	protected Object sender = null;
	/**
	 * The current delivery path for the notification. Updated as the event
	 * works though the delivery system.
	 */
	protected int deliveryPath = DIRECT;
	/**
	 * Default constructor.
	 */
	public NotificationEvent( )
	{
	}
	/**
	 * Convenience constructor that specifies the target element.
	 * 
	 * @param obj
	 *            the target element.
	 */
	public NotificationEvent( DesignElement obj )
	{
		target = obj;
	}
	/**
	 * Returns the delivery path by which the event was sent to the listener.