The tiny community of Magnolia Springs snuggles its oak-lined streets against the banks of the gentle Magnolia River.  Roughly 15 miles from either Fairhope or Gulf Shores, this spot has to be one of the best-kept secrets in Alabama.   That is why Winston Groom could pen “Forrest Gump” unhindered here; and Fannie Flagg could work on “Fried Green Tomatoes.”…