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/render/AxesRenderer.java
tre.setLabel( la );
		tre.setTextPosition( iLabelLocation );
		tre.setLocation( lo );
		final LineRenderEvent lre = (LineRenderEvent) ( (EventObjectCache) ipr ).getEventObject( StructureSource.createAxis( axModel ),
				LineRenderEvent.class );
		lre.setLineAttributes( lia );
		lre.setStart( LocationImpl.create( 0, 0 ) );
		lre.setEnd( LocationImpl.create( 0, 0 ) );
		
		final boolean bRendering3D = iDimension == IConstants.THREE_D;
		final boolean bRenderOrthogonal3DAxis = ( iWhatToDraw & IConstants.ORTHOGONAL_AXIS ) == IConstants.ORTHOGONAL_AXIS
				&& bRendering3D;
		final boolean bRenderBase3DAxis = ( iWhatToDraw & IConstants.BASE_AXIS ) == IConstants.BASE_AXIS
				&& bRendering3D;
		final boolean bRenderAncillary3DAxis = ( iWhatToDraw & IConstants.ANCILLARY_AXIS ) == IConstants.ANCILLARY_AXIS
				&& bRendering3D;
		final DeferredCache dc = getDeferredCache( );
		final int axisType = ax.getAxisType( );
		double[] daEndPoints3D = null;
		double[] da3D = null;
		Location3D lo3d = null;
		Text3DRenderEvent t3dre = null;
		Line3DRenderEvent l3dre = null;
		double dXStart = 0;
		double dZStart = 0;
		double dXEnd = 0;
		double dZEnd = 0;
		if ( iDimension == IConstants.THREE_D )
		{
			AllAxes aax = pwa.getAxes( );