Use dynamic schema info in UI

[BenjaminCharmes]

Use this information in the UI: e.g., when generating dynamic data table for a type, or when generating item pages. At least initially, this could just give a way to list custom fields that are missing from the edit page with generic components. e.g., if JSON schema type is a string: show it in a textarea, or if its a date, show it as a date. i.e., type-aware components. This might involve extending JSON schema types with some internal type-system that includes e.g., dates.