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
* @param prop
		 *            the definition of the property.
		 */
		public DataSetParametersPropertyHandle( DesignElementHandle element,
				ElementPropertyDefn prop )
		{
			super( element, prop );
		}
		/**
		 * Constructs the handle for a top-level property with the given element
		 * handle and property name.
		 * 
		 * @param element
		 *            a handle to a report element
		 * @param propName
		 *            the name of the property
		 */
		public DataSetParametersPropertyHandle( DesignElementHandle element,
				String propName )
		{
			super( element, propName );
		}
		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.birt.report.model.api.SimpleValueHandle#removeItem(int)
		 */
		public void removeItem( int posn ) throws PropertyValueException
		{
			DataSetParameterHandle paramHandle = (DataSetParameterHandle) getAt( posn );