Backend refactor

Since the rewrite from PHP to Django, the backend hasn’t had big refactoring because it did what it had to do, and was very stable. The choice for backbone/knockout in combination with by Django generated forms did always felt somewhat ugly, but time to go fully API was a bridge too far.

Now, having getting to known DRF’s viewsets a lot better, I’ve created a base viewset that can serve the currect frontend while removing all CBVs, most templates, and a lot of JavaScript.

One Django app is now completely done like this (and propperly tested, which wasn’t the case before *cough*), so I’ll continue this refactor throughout the rest of the apps.

With the new viewsets in place, the frontend can also be rewriten from backbone/knockout to Angular2/TypeScript.