Bug 150347 Support binary stream as preview image.
See 144843. We need model to save binary strame as report preview image. Currently, preview image is an external image. Maybe need a type to distinguish preview image type.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/writer/DesignWriter.java
*            the object to write
	 */
	public void visitReportDesign( ReportDesign obj )
	{
		writer.startElement( DesignSchemaConstants.REPORT_TAG );
		super.visitReportDesign( obj );
		property( obj, ReportDesign.REFRESH_RATE_PROP );
		property( obj, Module.INITIALIZE_METHOD );
		property( obj, ReportDesign.BEFORE_FACTORY_METHOD );
		property( obj, ReportDesign.AFTER_FACTORY_METHOD );
		property( obj, ReportDesign.BEFORE_RENDER_METHOD );
		property( obj, ReportDesign.AFTER_RENDER_METHOD );
		property( obj, IModuleModel.THEME_PROP );
		resourceKey( obj, DesignElement.DISPLAY_NAME_ID_PROP,
				DesignElement.DISPLAY_NAME_PROP );
		property( obj, ReportDesign.ICON_FILE_PROP );
		property( obj, ReportDesign.CHEAT_SHEET_PROP );
		property( obj, ReportDesign.EVENT_HANDLER_CLASS_PROP );
		
		writeStructureList( obj, ReportDesign.LIBRARIES_PROP );
		writeSimpleStructureList( obj, ReportDesign.INCLUDE_SCRIPTS_PROP,
				IncludeScript.FILE_NAME_MEMBER );
		
		writeStructureList( obj, ReportDesign.CONFIG_VARS_PROP );
		writeContents( obj, ReportDesign.TEMPLATE_PARAMETER_DEFINITION_SLOT,
				DesignSchemaConstants.TEMPLATE_PARAMETER_DEFINITIONS_TAG );
		writeArrangedContents( obj, ReportDesign.PARAMETER_SLOT,
				DesignSchemaConstants.PARAMETERS_TAG );
		writeArrangedContents( obj, ReportDesign.DATA_SOURCE_SLOT,
				DesignSchemaConstants.DATA_SOURCES_TAG );