change BasicService methods API

[MikhailDeriabin]

• [x] Make all methods in IService and BasicSerivce to return a tuple, where first item is data or null, and second an array of ServiceErrors or null if no errors
• [x] Change all files that are using this service
• [x] Change, if needed, decorators, which are relying on it. So that they are expecting to get tupple, thrown APIError/ServiceError or returned APIError/ServiceError
• [x] Check that everything still works