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
{
	/**
	 * The low-level writer that emits XML syntax.
	 */
	/**
	 * The constant for default model name space.
	 */
	final protected static String DEFAULT_NAME_SPACE = "http:www.eclipse.org/birt/2005/design"; 
	/**
	 * The XML writer.
	 */
	protected XMLWriter writer = null;
	/**
	 * The base 64 codec for embedded images.
	 */
	protected static Base64 base = new Base64( );
	/**
	 * The compatibility to create bound columns.
	 */
	protected BoundColumnsWriterMgr boundColumnsMgr = null;
	/**
	 * Control flag indicating whether need mark line number.
	 */
	protected boolean markLineNumber = true;
	/**