Simple suggestions

I’m doing this with filter, but maybe that should go into plugin:

	$friendly_filename = str_replace('-.', '.', $friendly_filename); // Remove - at the end (before dot)
	$friendly_filename = str_replace('_.', '.', $friendly_filename); // Remove _ at the end (before dot)
	
	$friendly_filename = preg_replace('/-+/', '-', $friendly_filename); // Remove multiple -
	$friendly_filename = preg_replace('/_+/', '_', $friendly_filename); // Remove multiple _