The local baseball shrine just celebrated a significant birthday. Maybe you heard? But underneath all the hoopla that just managing to hang around for a century buys you, Fenway Park actually does deserve special attention this year for some low-key additions scattered throughout the stadium. They won’t ever compete with the Green Monster seats, but the exhibits that officially constitute “Fenway Park: A Living Museum” offer a pretty cool combination of park timelines and treasures, baseball memorabilia, and American history.