SAVANNAH, Ga.—Bill Howard’s family has earned a living from the piney woods of southeast Georgia since 1898, when his great-grandfather and seven great-great uncles started cutting lumber with a portable sawmill.  Over four generations, the Howards built a permanent mill in Statesboro, Ga., and added timberland to feed it. Today the family employs roughly 300 people between the sawmill, two other plants and three builder-supply yards.   The collapse of pulpwood markets in the region is threatening the prospects of a fifth generation working the woods.  The South, and Georgia in particular, have borne the brunt of a historic run of…