Bug 200471 Add "need not sort for grouping" option in report item
Currently when Data engine proceeds groups, it always sorts the result set according to given group key.However that should not be necessary when the raw data is already sorted. So we'd like to add new options so that user can indicate whether should we sort the data before grouping. In model, we should allow user to set a "need not do sort for grouping" option to all the report element that can be grouped(table, list,etc.)
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/elements/interfaces/IListingElementModel.java
* Name of the on-start property. Script called before the first row is
	 * retrieved from the data set for this element. Called after the data set
	 * is open but before the header band is created.
	 * 
	 * @deprecated
	 */
	public static final String ON_START_METHOD = "onStart"; 
	/**
	 * Name of the on-row property. Script called for each row retrieved from
	 * the data set for this element, but before creating any content for that
	 * row.
	 * 
	 * @deprecated
	 */
	public static final String ON_ROW_METHOD = "onRow"; 
	/**
	 * Name of the on-finish property. Script called after the last row is read
	 * from the data set for this element, but before the footer band is
	 * created.
	 * 
	 * @deprecated
	 */
	public static final String ON_FINISH_METHOD = "onFinish"; 
	
	/**
	 * Name of the repeat header property.
	 */
	public static final String REPEAT_HEADER_PROP = "repeatHeader"; 
}