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
property( obj, IParameterGroupModel.START_EXPANDED_PROP );
		resourceKey( obj, IParameterGroupModel.HELP_TEXT_KEY_PROP,
				IParameterGroupModel.HELP_TEXT_PROP );
		property( obj, ICascadingParameterGroupModel.DATA_SET_PROP );
		property( obj, ICascadingParameterGroupModel.PROMPT_TEXT_PROP );
		property( obj, ICascadingParameterGroupModel.DATA_SET_MODE_PROP );
		writeContents( obj, IParameterGroupModel.PARAMETERS_SLOT,
				DesignSchemaConstants.PARAMETERS_TAG );
		writeOverridenPropertyValues( obj );
		writer.endElement( );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.elements.ElementVisitor#visitScalarParameter(org.eclipse.birt.report.model.elements.ScalarParameter)
	 */
	public void visitScalarParameter( ScalarParameter obj )
	{
		
		boundColumnsMgr.dealScalarParameter( obj, getModule( ) );
		writer.startElement( DesignSchemaConstants.SCALAR_PARAMETER_TAG );
		super.visitScalarParameter( obj );
		property( obj, IScalarParameterModel.VALUE_TYPE_PROP );
		property( obj, IScalarParameterModel.DATA_TYPE_PROP );
		property( obj, IScalarParameterModel.PARAM_TYPE_PROP );
		resourceKey( obj, IScalarParameterModel.PROMPT_TEXT_ID_PROP,
				IScalarParameterModel.PROMPT_TEXT_PROP );
		property( obj, IScalarParameterModel.LIST_LIMIT_PROP );
		property( obj, IScalarParameterModel.CONCEAL_VALUE_PROP );
		property( obj, IScalarParameterModel.IS_REQUIRED_PROP );