Add license submitter info

If you go to `http://localhost:6543/contents/e79ffde3-7fb4-4af3-9ec8-df648b391597@1.6`, it used to show license and submitter like this:

```
"license": "http://creativecommons.org/licenses/by/3.0/",
"submitter": "e5a07af6-09b9-4b74-aa7a-b7510bee90b8",
```

But webview needs more information than this, so this pull request changes the API to return the following:

```
"license": {"url": "http://creativecommons.org/licenses/by/3.0/", "code": "by", "version": "3.0", "name": "Attribution"},
"submitter": {"website": null, "surname": null, "suffix": null, "firstname": "OpenStax College", "title": null, "othername": null, "email": "info@openstaxcollege.org", "fullname": "OpenStax College", "id": "e5a07af6-09b9-4b74-aa7a-b7510bee90b8"},
```