Create UserCustomField object from a User object

[RoyalScribblz]

Is your feature request related to a problem? Please describe.
UserCustomField's have HasPic, PicHash, and Value attributes that are not on User object, so I can't simply copy across.

Describe the solution you'd like
A constructor overload that you can pass a user into, new UserCustomField(user).

Describe alternatives you've considered

new UserCustomField
 {
    Id = user.Id,
    Name = user.Name,
    Email = user.Email,
    ActiveFlag = user.ActiveFlag,
    HasPic = user.IconUrl is null or "",
    PicHash = null,  // could get the image and get hash but not sure what hashing function
    Value = null  // no clue what this value is
 };