Fix coverage data collection

http://hydra.nixos.org/build/3253046
dhcpcd: Don't duplicate log messages

Dhcpcd writes log messages to both syslog and stderr.  So ignore
stderr.
dhcpcd: Go into the background immediately
Order mkfs services before the corresponding fsck services
Make Apache wait for ‘charon send-keys’

(This is a no-op on non-Charon deployments since the ‘keys.target’
unit won't have any dependencies.)
Fix description
dhcpcd: Don't use --background so that fetch-ec2-data can be ordered after it
wpa_supplicant.nix: Slightly improve descriptions
Remove outdated comment about EC2 booting into stage-2 directly
Turn networking.interfaces into an attribute set

Thus

  networking.interfaces = [ { name = "eth0"; ipAddress = "192.168.15.1"; } ];

can now be written as

  networking.interfaces.eth0.ipAddress = "192.168.15.1";

The old notation still works though.
Turn fileSystems into an attribute set

So now you can write

  fileSystems =
    [ { mountPoint = "/";
        device = "/dev/sda1";
      }
    ];

as

  fileSystems."/".device = "/dev/sda1";
Adding quick instructions in system-tarball-pc to use it as chroot.

I also split the readme into a file apart.
pam: Add default configuration for GNU screen.

This is needed in order to properly lock your screen using the C-a C-x
(lockscreen) command _and_ being back to re-login, because the "other" PAM
service/fallback is to deny authentication.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
pam: Douchebag commit, fix alphabetical order.

Yes, I'm going to get back to school and learn the alphabet. I promise!

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
xsession: source /etc/profile at the beginning of the script

The xsession script runs services that depend on a sane environment. Gpg-agent, for
example, runs the program "pinentry-gtk-2" to obtain the password to unlock GnuPG
and SSH keys. That program will display only gibberish unless $FONTCONFIG_FILE is
configured properly. Instead of configuring these variables explicitly one by one,
we just source /etc/profile, which contains the appropriate @shellInit@ code.
systemd: Fail if kernel features are missing.

This has rendered my system unbootable, because I forgot to enable AUTOFS4 in my
custom kernel. In addition to AUTOFS4, this includes (hopefully) all other
kernel features needed by systemd, as listed in the README:

REQUIREMENTS:
  Linux kernel >= 2.6.39
    with devtmpfs
    with cgroups (but it's OK to disable all controllers)
    optional but strongly recommended: autofs4, ipv6

Autofs4 is not a requirement here, but in our case it turns out that the system
is not able to boot properly with a LUKS-enabled system (or at least not on _my_
system).

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
firewall.nix: Don't fail if IPv6 is disabled
Remove unnecessary toPath that breaks with recent nixUnstable
modules/programs/bash/bash.nix: cosmetic indention fix
Add option "environment.binsh" to configure the shell executable used to create the global /bin/sh symlink.