Merge pull request #634 from PhpMadman/RefSort

[*] FO : Sort by Product reference

themes/default/mobile/category-product-sort.tpl

@@ -64,6 +64,8 @@
 				{if $PS_STOCK_MANAGEMENT && !$PS_CATALOG_MODE}
 					<option value="quantity:desc" {if $orderby eq 'quantity' AND $orderway eq 'desc'}selected="selected"{/if}>{l s='In stock'}</option>
 				{/if}
+				<option value="reference:asc" {if $orderby eq 'reference' AND $orderway eq 'asc'}selected="selected"{/if}>{l s='Reference: Lowest first'}</option>
+				<option value="reference:desc" {if $orderby eq 'reference' AND $orderway eq 'desc'}selected="selected"{/if}>{l s='Reference: Highest first'}</option>
 			</select>
 		</form>
 	</div> <!-- .{$container_class} -->