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/writer/ModuleWriter.java
}
	/**
	 * Writes the resource key.
	 * 
	 * @param obj
	 *            the design element
	 * @param resourceKey
	 *            the property name of resource key
	 * @param resourceName
	 *            the property name of user-visible resource
	 * @param cdata
	 *            whether the values is written as CDATA
	 */
	protected void resourceKey( DesignElement obj, String resourceKey,
			String resourceName, boolean cdata )
	{
		PropertyDefn nameProp = (ElementPropertyDefn) obj.getDefn( )
				.getProperty( resourceName );
		assert nameProp != null;
		Object value = obj.getLocalProperty( getModule( ), nameProp.getName( ) );
		String xml = nameProp.getXmlValue( getModule( ), value );
		PropertyDefn keyProp = (ElementPropertyDefn) obj.getDefn( )
				.getProperty( resourceKey );
		assert keyProp != null;
		value = obj.getLocalProperty( getModule( ), keyProp.getName( ) );
		String xmlKey = keyProp.getXmlValue( getModule( ), value );
		if ( xmlKey == null && xml == null )
			return;
		if ( nameProp.getTypeCode( ) == IPropertyType.HTML_TYPE )
		{