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
* @see #getDataSource()
	 */
	public void setDataSource( String name ) throws SemanticException
	{
		setStringProperty( ISimpleDataSetModel.DATA_SOURCE_PROP, name );
	}
	/**
	 * Returns an iterator over the list of output parameter definitions. The
	 * iterator returns instances of <code>DataSetParameterHandle</code> that
	 * represents parameter objects.
	 * 
	 * @return iterator over output parameter definitions.
	 * @see org.eclipse.birt.report.model.api.elements.structures.DataSetParameter
	 */
	public Iterator parametersIterator( )
	{
		PropertyHandle propHandle = getPropertyHandle( IDataSetModel.PARAMETERS_PROP );
		assert propHandle != null;
		return propHandle.iterator( );
	}
	/**
	 * Returns an iterator over the list of parameter bindings. The iterator
	 * returns instances of <code>ParamBindingHandle</code> that represents
	 * parameter binding object.
	 * 
	 * @return iterator over parameter binding.
	 * 
	 * @see org.eclipse.birt.report.model.api.elements.structures.ParamBinding
	 */
	public Iterator paramBindingsIterator( )