Bug 104986 Backgound image uses an absolute path
Currently Chart uses an absolute path to indicate a backgournd image, that may cause the design unusable on other environments. Expected the background image can be definded in multiple ways like in report designer. e.g. URI(absolute path), File(relative path), Embedded Image(Encoded Image Data).
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/model/attribute/AttributePackage.java
* @see java.lang.String
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getID()
	 * @generated
	 */
	int ID = 82;
	/**
	 * The meta object id for the '<em>Intersection Type Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.IntersectionType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getIntersectionTypeObject()
	 * @generated
	 */
	int INTERSECTION_TYPE_OBJECT = 83;
	/**
	 * The meta object id for the '<em>Leader Line Style Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.LeaderLineStyle
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getLeaderLineStyleObject()
	 * @generated
	 */
	int LEADER_LINE_STYLE_OBJECT = 84;
	/**
	 * The meta object id for the '<em>Legend Behavior Type Object</em>' data type.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.LegendBehaviorType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getLegendBehaviorTypeObject()
	 * @generated
	 */
	int LEGEND_BEHAVIOR_TYPE_OBJECT = 85;