> `GroupValues` could possibly use an `byte[]`, where each field is an index in the array. Something like:
- 0 = unset
- 1 = field has value 1
- -1 = field has value 0
All that is needed then is for a good way of connecting a field to an integer. In worst case, this can be done with `Map<T, Integer>` but I hope for another solution. Perhaps create some `Wrapped<T>` with the T and an int.