Add some clarifications to API for exercises
Add some clarifications to API for exercises

petervanderdoes/wger,rolandgeider/wger,DeveloperMal/wger,wger-project/wger,petervanderdoes/wger,rolandgeider/wger,wger-project/wger,rolandgeider/wger,wger-project/wger,kjagoo/wger_stark,petervanderdoes/wger,kjagoo/wger_stark,DeveloperMal/wger,DeveloperMal/wger,kjagoo/wger_stark,wger-project/wger,kjagoo/wger_stark,DeveloperMal/wger,rolandgeider/wger,petervanderdoes/wger