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/impl/AttributePackageImpl.java
{
		super( eNS_URI, AttributeFactory.eINSTANCE );
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	private static boolean isInited = false;
	/**
	 * Creates, registers, and initializes the <b>Package</b> for this
	 * model, and for any others upon which it depends.  Simple
	 * dependencies are satisfied by calling this method on all
	 * dependent packages before doing anything else.  This method drives
	 * initialization for interdependent packages directly, in parallel
	 * with this package, itself.
	 * <p>Of this package and its interdependencies, all packages which
	 * have not yet been registered by their URI values are first created
	 * and registered.  The packages are then initialized in two steps:
	 * meta-model objects for all of the packages are created before any
	 * are initialized, since one package's meta-model objects may refer to
	 * those of another.
	 * <p>Invocation of this method will not affect any packages that have
	 * already been initialized.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see #eNS_URI
	 * @see #createPackageContents()
	 * @see #initializePackageContents()
	 * @generated
	 */
	public static AttributePackage init( )