By Alasdair Fotheringham LAGO DE SANABRIA, Spain, Aug 28 (Reuters) - Australian Michael Matthews recorded a stage win in the first week of his maiden Grand Tour on Wednesday after a chaotic bunch sprint finish to the fifth stage of the Tour of Spain. The 22-year-old Orica-GreenEdge rider, a former under-23 world champion, outsprinted Argentina's Maximiliano Richeze and Belgian Gianni Meersman in a dash for the line at Lago de Sanabria. Italian Vincenzo Nibali, the favourite for outright victory in Madrid on Sept. ... More...