makes value a derived property

This is important if you ever want to be able to have a calculated value that's different than what's in the text input.

For example, i made a validated address field, that takes a free-form address input, checks it against an API and if there's a match, returns the entire matched object data. in that case the matched data is an object of properties and needs to be the `value` for this input field. This change makes that possible.