Revert "GeographyApp.Domain.CityManager.Add() method deleted and ICityManager, CountryService classes updated. GeographyApp.Domain.CountryManager.Add() method updated."

This reverts commit 83e0bca35a8cf2fd8fcd88be5e204b3473d71559.
CounryService.Add() method updated.
GeographyApp.Domain.CityManager.Add() method deleted.
ICityManager interface updated.
GeographyApp.Domain.CountryManager.Add() & GeographyApp.Domain.CountryManager.Update() methods updated.