[WIP] Improve printing experience and update related packages

This is my effort to improve printing for me and update packages while I'm at it. It consists of:
* updating cups to 2.0
* adding patch that allows to use multifunctional devices with it (fixing access rights)
* updating ghostscript and dropping GNU fork (looks like its development has been discontinued)
* adding cups-filters and other required infrastructure for the new cups
* (not yet looked at) making cups show all available printer drivers when adding new printer.

It's related to #4680 and #4711 .

I wanted to ask for a Hydra jobset, since my home server seems to be too weak for rebuilding everything dependent on cups and stuff (building for half a day and it's stuck on one of chromiums for 4hrs already, with chromiumDev yet on its way).