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/AttributeFactoryImpl.java
{
		switch ( eClass.getClassifierID( ) )
		{
			case AttributePackage.ACTION_VALUE :
				return createActionValue( );
			case AttributePackage.ANGLE3_D :
				return createAngle3D( );
			case AttributePackage.AXIS_ORIGIN :
				return createAxisOrigin( );
			case AttributePackage.BOUNDS :
				return createBounds( );
			case AttributePackage.CALL_BACK_VALUE :
				return createCallBackValue( );
			case AttributePackage.COLOR_DEFINITION :
				return createColorDefinition( );
			case AttributePackage.DATA_POINT :
				return createDataPoint( );
			case AttributePackage.DATA_POINT_COMPONENT :
				return createDataPointComponent( );
			case AttributePackage.DATE_FORMAT_SPECIFIER :
				return createDateFormatSpecifier( );
			case AttributePackage.EXTENDED_PROPERTY :
				return createExtendedProperty( );
			case AttributePackage.FILL :
				return createFill( );
			case AttributePackage.FONT_DEFINITION :
				return createFontDefinition( );
			case AttributePackage.FORMAT_SPECIFIER :
				return createFormatSpecifier( );
			case AttributePackage.GRADIENT :