Multi-file JSONs

This release is the first to include the multi-file JSON directory structure. It also includes a better datapackage.json file thanks to @davbre.

It also contains modifications to how we identify parties, now including a GUID instead of their internal ID, which is not unique across the dataset.

Teenie Harris files are now also linking to the larger versions of themselves.

GUID release

We have modified the dataset to use GUIDs for the item IDs instead of our internal identifiers.

Adding a DOI

This is a minor release, just to trigger the DOI generation.