Consider adding overloads of IsInRole(Async) and other methods which accept user id

The old version of ASP.NET Identity had a lot of overloads of different methods that accepted user id instead of user object. In the current version only the User object overloads are left. This forces us to write code like this

`UserManager.IsInRoleAsync(new User { Id = userId }, "Admin");`

Please consider adding the overloads that accept userId.