By Silke Koltrowitz and Maytaal Angel ZURICH/LONDON (Reuters) -Nestle said on Thursday it will start paying cocoa farmers cash if they send their children to school rather than out to tend crops as part of a push to purchase all of its cocoa through a fully traceable, directly sourced supply chain by 2025. Chocolate makers are coming under mounting pressure from investors, consumers and governments to make sure the cocoa beans they source are not produced using child labour or in illegal cocoa plantations in protected forests, both of which are common in West Africa. The food group behind KitK…