Web+: set a group name for download notifications

It is not clear that these come from Web+ otherwise (since they use the
downloaded file icon rather than the app one).

src/apps/webpositive/DownloadProgressView.cpp

@@ -626,6 +626,7 @@ DownloadProgressView::DownloadFinished()
 	fStatusBar->SetBarColor(ui_color(B_SUCCESS_COLOR));
 
 	BNotification success(B_INFORMATION_NOTIFICATION);
+	success.SetGroup(B_TRANSLATE("WebPositive"));
 	success.SetTitle(B_TRANSLATE("Download finished"));
 	success.SetContent(fPath.Leaf());
 	BEntry entry(fPath.Path());
@@ -648,6 +649,7 @@ DownloadProgressView::CancelDownload()
 		// Also cancel the download
 		fDownload->Cancel();
 		BNotification success(B_ERROR_NOTIFICATION);
+		success.SetGroup(B_TRANSLATE("WebPositive"));
 		success.SetTitle(B_TRANSLATE("Download aborted"));
 		success.SetContent(fPath.Leaf());
 		// Don't make a click on the notification open the file: it is not