subtask of T95002

this is to change/update all the font packages / package names to be able to apply the mediawiki module (with ./manifests/packages/fonts.pp) on jessie.

The ttf-* prefix has been replaced by fonts-* in Debian (and subsequently, Ubuntu) and has been rolled out gradually.
The way this works is that one release leaves the old package name but with an empty package depending on the corresponding replacement (a so-called transitional package). The transitional packages stay for a release, then get dropped. wheezy had some of those, as you can e.g. see here.