The City in the Forest hopes to get back to its roots.Despite its reputation as a city of wall-to-wall subdivisions, office complexes, and shopping centers, Atlanta's not a complete stranger to matters of green. At the time of its mid-19th century founding, in the woods at the end of a railroad line, it was called the "City in the Forest." And in the early 20th century, the city created the 185-acre Piedmont Park in Midtown (currently ballooning to add another 50 acres). Since then, of course, the Atlanta of urban planning lore has descended: traffic-choked, overdeveloped, polluted, with a major …