Use font-types in norad?

[rsheeter]

From #272 (comment).

+1 from me, only concern is I think we want any font-types dependence on serde to be optional.

[cmyr]

I looked into this quickly and it's not totally obvious that there are many places this would make sense. The obvious one is the Tag type in designspaces, and maybe the various table-specific fields on fontinfo.plist; the problem with this second case is that while these do map to specific values in the tables, the UFO spec often specifies them in different formats; for instance the openTypeHeadCreated field is a string, not a LongDateTime.

[madig]

I think UFO is using more general types on purpose, because the original goal was to encompass more than OpenType.

[cmyr]

That's a very reasonable goal I think.