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
* 
	 * @generated
	 * @ordered
	 */
	int FONT_DEFINITION__ITALIC = 3;
	/**
	 * The feature id for the '<em><b>Strikethrough</b></em>' attribute.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int FONT_DEFINITION__STRIKETHROUGH = 4;
	/**
	 * The feature id for the '<em><b>Underline</b></em>' attribute. <!--
	 * begin-user-doc --> <!-- end-user-doc -->
	 * 
	 * @generated
	 * @ordered
	 */
	int FONT_DEFINITION__UNDERLINE = 5;
	/**
	 * The feature id for the '<em><b>Word Wrap</b></em>' attribute. <!--
	 * begin-user-doc --> <!-- end-user-doc -->
	 * 
	 * @generated
	 * @ordered
	 */
	int FONT_DEFINITION__WORD_WRAP = 6;
	/**
	 * The feature id for the '<em><b>Alignment</b></em>' containment reference.