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
* Returns the module to write.
	 * 
	 * @return the module to write
	 */
	abstract protected Module getModule( );
	/**
	 * Writes the report design to a file.
	 * 
	 * @param outputFile
	 *            output file into which to write the design
	 * 
	 * @throws IOException
	 *             if a write error occurs
	 */
	public void write( File outputFile ) throws IOException
	{
		
		ModuleOption options = getModule( ).getOptions( );
		if ( options != null )
			markLineNumber = options.markLineNumber( );
		writer = new IndentableXMLWriter( outputFile, getModule( )
				.getUTFSignature( ), markLineNumber );
		writeFile( );
		writer.close( );
	}
	/**
	 * Writes the report design to the output stream.
	 * 
	 * @param os
	 *            the output stream to which the design is written.