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/api/DataSetHandle.java
implements
			IDataSetModel,
			ISimpleDataSetModel
{
	/**
	 * Constructs a data set handle with the given design and element. The
	 * application generally does not create handles directly. Instead, it uses
	 * one of the navigation methods available on other element handles.
	 * 
	 * @param module
	 *            the module
	 * @param element
	 *            the model representation of the element
	 */
	public DataSetHandle( Module module, DesignElement element )
	{
		super( module, element );
	}