Don't expand paths during VirtualBox image generation
Add the demo user to the vboxsf group to allow mounting of shared folders
Only start the VirtualBox guest services if we're in a VirtualBox VM
Add more video drivers to the VM image

This might allow it to work in VMware and QEMU.
Make it easier to define timer units for services

Systemd services now have a startAt attribute.  If set, NixOS will
automatically emit a timer unit that causes the service to start at
the specified time.  For example:

  systemd.services.foo =
    { script = "... bla bla ...";
      startAt = "02:15";
    };

causes the given script to be started at 02:15 every day.
Fix eval error
Move all of NixOS to nixos/ in preparation of the repository merge
Merge the NixOS repository into Nixpkgs
Move pkgs/lib/ to lib/
Fix references to pkgs/lib
Unify the Nixpkgs and NixOS version numbers
Update the release expressions and the channel generators
nixos-checkout: Only fetch the Nixpkgs repo
Merge .gitignore files
Fix setting of .version-suffix