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
else
		{
			for ( int i = 0; i < children.size( ); i++ )
			{
				ContentNode child = (ContentNode) children.get( i );
				writeContentNode( child );
			}
		}
		writer.endElement( );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.elements.ElementVisitor#visitCube(org.eclipse.birt.report.model.elements.olap.Cube)
	 */
	public void visitCube( Cube obj )
	{
		super.visitCube( obj );
		property( obj, ICubeModel.DEFAULT_MEASURE_GROUP_PROP );
		writeStructureList( obj, ICubeModel.FILTER_PROP );
		writeContents( obj, ICubeModel.DIMENSIONS_PROP );
		writeContents( obj, ICubeModel.MEASURE_GROUPS_PROP );
		writeContents( obj, ICubeModel.ACCESS_CONTROLS_PROP );
		writeOverridenPropertyValues( obj );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.elements.ElementVisitor#visitDimension(org.eclipse.birt.report.model.elements.olap.Dimension)
	 */