[Tails-dev] Please review and merge web/delete-forum

I finished a second round of cleaning the forum and there's nothing in
/forum anymore! This happened in the master branch already but getting
rid of wiki/src/forum also implied more infrastructural changes. This is
what this branch is about.

So please review and merge into master.

Probably we also have to notify root@??? about the changes to
ikiwiki.setup.

--
sajolida