Bug 213126 Add support for DataEngine-leve dataset cache
In many cases the DataEngine-leve dataset cache is useful which ensure that a dataset is executed one time during rendering one report. To support this feature a new dataset property should be added. The Birt customer can choose whether this dataset need to be cached or not by setting the property in deisgn time.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/writer/ModuleWriter.java
public void visitImage( ImageItem obj )
	{
		
		boundColumnsMgr.dealImage( obj, getModule( ) );
		writer.startElement( DesignSchemaConstants.IMAGE_TAG );
		super.visitImage( obj );
		property( obj, IImageItemModel.SIZE_PROP );
		property( obj, IImageItemModel.SCALE_PROP );
		property( obj, IImageItemModel.SOURCE_PROP );
		String source = (String) obj.getLocalProperty( getModule( ),
				IImageItemModel.SOURCE_PROP );
		if ( DesignChoiceConstants.IMAGE_REF_TYPE_URL.equalsIgnoreCase( source )
				|| DesignChoiceConstants.IMAGE_REF_TYPE_FILE
						.equalsIgnoreCase( source ) )
		{
			property( obj, IImageItemModel.URI_PROP );
		}
		else if ( DesignChoiceConstants.IMAGE_REF_TYPE_EMBED
				.equalsIgnoreCase( source ) )
		{
			property( obj, IImageItemModel.IMAGE_NAME_PROP );
		}
		else if ( DesignChoiceConstants.IMAGE_REF_TYPE_EXPR
				.equalsIgnoreCase( source ) )
		{
			property( obj, IImageItemModel.TYPE_EXPR_PROP );
			property( obj, IImageItemModel.VALUE_EXPR_PROP );
		}
		resourceKey( obj, IImageItemModel.ALT_TEXT_KEY_PROP,
				IImageItemModel.ALT_TEXT_PROP );