African women need to up their games in their respective trades. Forbes Africa has released its annual list of dollar-billionaires on the continent, and in total, 18 very wealthy citizens make it into this exclusive club, all men. Nigerian Aliko Dangote remains the richest man in Africa, with his fortune pushing the $14 billion mark. The cement and sugar production magnate has a comfortable cushion at the top of the tree, and there’s daylight between him and Johann Rupert. The Stellenbosch-based billionaire is second on the list, with $11 billion in the bank. Another South African, Nicky Oppen…