sysklogd: Don't remove /dev/log when syslogd exits

This messes up systemd-journald.
Adding a KDE wrapper, to easily have KDE programs in nix-env.

Specially for those not running KDE.
kdewrapper: fixes in env vars
Adding pygobject3 (for bluez4).

bluez-simple-agent fails to work otherwise.
We discussed this a bit on #486, and this looks like the simplest way to
get bluez-simple-agent again.
Update Racket: patch by Karn Kallio