F# can upcast types to `obj` if those types are used in place. However, a `string seq` (`IEnumerable<string>` in C#) cannot be upcast to an `obj seq` (`IEnumerable<object>`) without mapping each item in the sequence. Making the `Field` constructor functions generic will allow them to take any object type, and these functions handle the conversion to `obj` (for `In` and `InArray`; others work transparently).
Reviewed-on: #8
Daniel J. Summers
740767661c
