Bug 137917 ImageHandle add setFile method.
According to new Resource Deployment Specification, image builder add a new image type 'File', so ImageHandle should add 'setFile' method as other type methods such as 'setURI'.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ImageHandle.java
*            the model representation of the element
	 */
	public ImageHandle( Module module, DesignElement element )
	{
		super( module, element );
	}
	/**
	 * Returns the image scale. The scale factor for the image given as a
	 * percentage.
	 * 
	 * @return the scale of this image.
	 */
	public double getScale( )
	{
		return getFloatProperty( ImageItem.SCALE_PROP );
	}
	/**
	 * Returns the image size. The size must be the internal name that is one
	 * the following options defined in <code>DesignChoiceConstants</code>:
	 * 
	 * <p>
	 * <ul>
	 * <li><code>IMAGE_SIZE_SIZE_TO_IMAGE</code>
	 * <li><code>IMAGE_SIZE_SCALE_TO_ITEM</code>
	 * <li><code>IMAGE_SIZE_CLIP</code>
	 * </ul>
	 * 
	 * @return the internal value of the image size.
	 */
	public String getSize( )