Bug 119220 Image in library can't display properly when it is imported in a report design.
Description: Image in library can't display properly when it is imported in a report design. Steps to reproduce: 1. Add an image in a library. 2. Use this library in a report design. 3. Drag the image from library explorer into layout view. 4. The image is marked invalid.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ImageHandle.java
* Returns the image source type. This is one of the following options
	 * defined in <code>DesignChoiceConstants</code>:
	 * <p>
	 * <ul>
	 * <li><code>IMAGE_REF_TYPE_NONE</code>
	 * <li><code>IMAGE_REF_TYPE_URL</code>
	 * <li><code>IMAGE_REF_TYPE_FILE</code>
	 * <li><code>IMAGE_REF_TYPE_EXPR</code>
	 * <li><code>IMAGE_REF_TYPE_EMBED</code>
	 * </ul>
	 * 
	 * @return the image source type.
	 * 
	 */
	public String getSource( )
	{
		return getStringProperty( ImageItem.SOURCE_PROP );
	}
	/**
	 * Returns the image source type. This is one of the following options
	 * defined in <code>DesignChoiceConstants</code>:
	 * <p>
	 * <ul>
	 * <li><code>IMAGE_REF_TYPE_NONE</code>
	 * <li><code>IMAGE_REF_TYPE_URL</code>
	 * <li><code>IMAGE_REF_TYPE_FILE</code>
	 * <li><code>IMAGE_REF_TYPE_EXPR</code>
	 * <li><code>IMAGE_REF_TYPE_EMBED</code>
	 * </ul>
	 *