Make full article body available through API

Please make the article body available through the API. A tiny commit for me, a huge opportunity for Zeit.de and German journalism. :wink:

What kind of bad could realistically happen with the body available through the API that couldn't happen right now as well?

Of course this is rather a political problem than a technical one. But I love [starting conversations through pull requests](https://github.com/fraunhoferfokus/ogd-metadata/pull/3), so here we go.