Move licenses API docs to opendefinition.org

[chris48s]

One of the objectives of this visual refresh is to bring the look-and-feel of https://licenses.opendefinition.org/ into line with the current OKFN branding.

There are two long-standing issues at

• Stop being API and website and just be dataset licenses#45
• Merge https://github.com/okfn/licenses with this repo ... #7

where moving the API documentation out of the seperate site/repo and into the main Open Definition site/repo is discussed. These issues broadly seemed to gain some approval from the community but were never really actively worked on. Now seems like a good time to revive this plan though as by far the easiest approach to updating the styling there is to move that one page of content into this repo.

As such, I've grabbed the documentation from https://github.com/okfn/licenses/blob/master/index.html and moved it over to this site (updating where appropriate) and left all the JSON/data where it is. I've also submitted a companion PR over at okfn/licenses#93 replacing the index page on licenses.opendefinition.org with a client-side redirect to https://opendefinition.org/licenses/api/ (which doesn't exist yet, but will once this is merged).

This doesn't fully close either of the referenced issues as there was also some additional discussion there around changes to the API/data. I have not addressed these here.

[rufuspollock]

LGTM. Great to see this moving forward 👏 /cc @mlinksva