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 visitTableGroup( TableGroup obj )
	{
		writer.startElement( DesignSchemaConstants.GROUP_TAG );
		super.visitTableGroup( obj );
		writeContents( obj, IGroupElementModel.HEADER_SLOT,
				DesignSchemaConstants.HEADER_TAG );
		writeContents( obj, IGroupElementModel.FOOTER_SLOT,
				DesignSchemaConstants.FOOTER_TAG );
		writer.endElement( );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.design.elements.DesignVisitor#visitColumn(org.eclipse.birt.report.model.design.elements.TableColumn)
	 */
	public void visitColumn( TableColumn obj )
	{
		
		
		writer.startElement( DesignSchemaConstants.COLUMN_TAG );
		markLineNumber( obj );
		writer.attribute( DesignSchemaConstants.ID_ATTRIB, new Long( obj
				.getID( ) ).toString( ) );
		attribute( obj, DesignSchemaConstants.VIEW_ACTION_ATTRIB,
				IDesignElementModel.VIEW_ACTION_PROP );
		super.visitColumn( obj );
		property( obj, ITableColumnModel.WIDTH_PROP );
		property( obj, ITableColumnModel.REPEAT_PROP );
		property( obj, ITableColumnModel.SUPPRESS_DUPLICATES_PROP );
		writeStructureList( obj, ITableColumnModel.VISIBILITY_PROP );