- Moved Python, Rubt packages to pip, gem, left binary packages in apt.

- Moved some packages from pip to pip3 (it's time to move to Python3).
- Removed firefoxdriver, it's nonfree, somewhat out of date and brings
with it Python packages.
- Added VLC, gstreamer1.0-libav because Totem is flaky.
- Added gnupg2.
- Added graphviz for better slideshows with pandoc.
- Added libnss-systemd for continued work on nspawn.
- Added screen for connecting to serial consoles.