When your weekend refuge starts looking blah, try some quick techniques for punching things up.   Opening the cottage every spring always reveals a to-do list of projects. Docks that need a hammer and nail. Screens riddled with holes. Outhouses verging on catastrophic. And interior spaces that look drab, cluttered and dated. Many long-time family cottages could use a renovation or serious interior-design overhaul, but that’s not always in...