CHARLESTON, South Carolina (Reuters) - A unique culture maintained by African slave descendants along the U.S. southeastern Atlantic coast will be featured with a float in the presidential inaugural parade on Monday, a proud moment for a group once reticent to promote its heritage. To nab a spot in the festivities for President Barack Obama along Pennsylvania Avenue in Washington, those working to preserve the Gullah Geechee culture highlighted its ties to First Lady Michelle Obama's family roots. ...