Get rid of the {% include relative-baseurl.html %}

[tordans]

I don't see any reason what would be bad to follow the default Jekyll behaviour (with a current Jekyll version, see PR) and use absolute URLs everywhere.

The advantage is, we could get rid of all those {% include relative-baseurl.html %} includes that are cluttered all over the place.

If the absolute-url-idea is a problem, we could at least check if the include in _layouts/basic.html is not enough for all the other pages. IMO a variable only needs to be assigned once, not in every single file.