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
if ( tag != null )
			writer.conditionalStartElement( tag );
		 
		writer.attribute( DesignSchemaConstants.NAME_ATTRIB, containerInfor
				.getPropertyName( ) );
		
		
		
		Iterator iter = list.iterator( );
		while ( iter.hasNext( ) )
		{
			( (DesignElement) iter.next( ) ).apply( this );
		}
		if ( tag != null )
			writer.endElement( );
	}
	/**
	 * Writes the contents of a slot. The contents are enclosed in an optional
	 * list tag.
	 * 
	 * @param obj
	 *            the container element
	 * @param slot
	 *            the slot to write
	 * @param tag
	 *            the optional list tag that encloses the list of contents
	 */
	protected void writeContents( DesignElement obj, int slot, String tag )
	{
		markLineNumber( new ContainerContext( obj, slot ) );