Changes to display basals from new data model

@jebeck @kentquirk 

These are the changes required for tideline to be able to render basals from the new data model.
Yeah, I'd like it over in the `datetime.js` module, and without moment. I think the idea is we might end up having sundial depend on moment, but we'd like to keep it out of everywhere else if possible (so that we can switch it out for something better if we want, down the road). But I can do this if you want. LMK.