[UNITYSDK-150] Made IUser conform to API document

* Renamed IUser.DoCreate to IUser.Create
* Renamed IUser.DoLogin to IUser.Login
* Renamed IUser.DoLogout to IUser.Logout
* Added IUser.ChangeName
* Added IUser.ChangePassword
* Moved IRoar.WhoAmI to IUser.WhoAmI
* Removed IRoar.Login
* Removed IRoar.Logout
* Removed IRoar.Create
[UNITYSDK-147] Warnings displayed in the Unity's console