Move most of this to a static web page generator

We experience a lot of load on our web page and it would be a good point in time to move the whole wordpress setup to a static page generator like Hugo. The advantage of this is:

• no need to have a quite complex setup with PHP-FPM, apache and vagrant to achieve good performance
• no need to deal with cache invalidation on the server side, because the rendered stuff is what the web server serves and the kernel/web server itself takes care of caching and co
• don't abuse the wordpress import feature for the static pages like /jobs, /team, all the feature pages etc
• all the content in one place and not half of it in this git repo and the other half in the database
• getting a dev setup should then be easier - currently it involves a lot of manual steps to get the wordpress properly setup
• automatic deployments to a staging and a production server should be easier then (because no need to keep the blog posts & co in sync because they are only held available in code)

Remarks:

• some dynamic pages need to be in place, like the pricing form and the white paper form, but this should be feasible

cc @MariusBluem @Espina2 @jospoortvliet because we talked about it.