US President Barack Obama has signed into law an initiative aimed at bringing electricity to 50 million people in sub-Saharan Africa by 2020. The Electrify Africa Act of 2015 will give legal backing to Mr Obama's flagship Power Africa scheme, which is trying to improve access to electricity through public-private partnerships. It took nearly two years to be passed in both houses of the US Congress. About two-thirds of people in Africa do not have access to reliable power....