Web API + Sphinx

Documentation is available at https://geordi.readthedocs.org/en/api/. I linked it to my repo and branch temporarily to demonstrate how it works.
Since this uses `Item.get` it won't get the benefits of the joined load, which we'd want to preserve. Perhaps add an `includes` argument to `Item.get` which takes a list, presumably including 'item_links' and 'item_data', and if they're present adds the relevant joinedload clauses. Then `includes=['item_links','item_data']` can be passed here and no harm done! :)