Refactor data being passed into SpineItem

[msimmer]

https://github.com/triplecanopy/b-ber/blob/master/packages/b-ber-lib/src/SpineItem.js

The files and config data is initially parsed and creates spine items. The format of this data is inconsistent in places; it should be unified, and additional attributes should be added for ease-of-use further down the line