/// <summary>
/// Constructs an OrderKeeper with its necessary initial element (empty OrderKeepers aren't possible).
/// </summary>
/// <param name="initial">The first element to place in the ordering</param>
public OrderKeeper(T initial) : base()
{
Add((First = new Record <T>(this, default, 0UL)));
public Record(OrderKeeper <T> keeper, T item, ulong label, Record <T> previous, Record <T> next)
{
Keeper = keeper;
Item = item;
Label = label;
Previous = previous ?? keeper.First;
Next = next ?? keeper.First;
}