re #58 massive code formatting
re #58 Rewrited client app to React #58 // yoso internal app // in progress #60 // fixed
re #58 fetch setting(const response), switch added default opt.
re #58 client part(especially rebuilt api.js, all fetches, little edits in YourRequests/UpcomingRequests and fixed bugs in calendar and overview (add event, save, post, numbers)
re #58 Refactoring, every fetch moved to api.js
re #58 first version of react app