In Dar es Salaam, many people without formal addresses are denied access to services and a legal identity. But technology is set to change that Tuesday 22 September 2015 08.14 EDT Last modified on Tuesday 22 September 2015 09.36 EDT Johan Knols is used to getting unusual directions as he travels around rural Tanzania. “Usually, when I’m trying to find someone’s house, they’ll guide me by saying, ‘after the fourth tree, down the path to…