Restricted Combine row monitoring

[Jan Hülsmann]

I am not sure if this was intended but the following README.md example for monitoring row-level changes does not work anymore since the access level of these properties got changed to internal in 4b822c0.

let listener = Post.changePublisher(in: db).sink { change in
    print("Post IDs changed: \(change.primaryKeys ?? "all")")
    print(" Columns changed: \(change.columnNames ?? "all")")
}

[marcoarment]

Thanks! Fixed.