By Rachel Savage LONDON, July 15 (Reuters) - Central African Republic will start selling a cryptocurrency it says will be worth $21 million next week, it said on Friday, amid a wider rout in the industry and scepticism over the project's feasibility in a poorly connected, war-torn country. The "Sango Coin", described as a "national digital currency" will go on sale on July 21 with a minimum investment of...