At the moment, mediawiki virtual hosts are written down with a lot of repetitiveness inside huge files. We should change that so that each change is more transparent and more manageable and less error-prone, especially since we're going to transition to PHP7 shortly and we want to be able to change things quickly.
Since all mediawiki vhosts are very similar to each other, we could codify most of what we have right now within a `mediawiki::vhost` define, which will need to allow various parameters, such as:
- ServerName / ServerAliases
- the docroot
- secure redirect
this will also allow us to unify beta and production sites once an for all (see T1256)
We can then have all these site definition lie in the `sites-available` directory of apache2, and have one large file including all of them in `site-enabled`, for now.