This has been bugging me since basically forever: the howto/template
is not a template for the "howto" section (which is now poorly defined
anyways) at *all*. It's precisely the template for *services*, and
really just belongs there.

I've been hesitant in performing that rename for a long time. First
because GitLab wikis didn't support redirects (they do now, and we add
one here), but also because we probably link to the wiki-replica
version of this in a few places.

I've tried to fix the links inside the wiki, but there are certainly
others that will break. We'll fix those as we go.

For now it seems better and more intuitive to have this at the right
place than preserve the legacy location.