Two prominent board members of the Atlanta BeltLine Partnership turned in their resignations Monday, saying not enough emphasis is being given to the issues of equity and affordability. The two board members are: Ryan Gravel, an urban planner who initially proposed the concept of the BeltLine in his Georgia Tech Master’s thesis; and Nathaniel Smith, founder of the Partnership for Southern Equity. They sent their letter of resignation to the chairman of the Partnership – Mike Donnelly, an executive…