common: Rename environment.nix to nix.package.

This is because environment.nix is now obsolete in current <nixpkgs>.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
common: Switch displayManager to lightdm.

Just a try as of now, not sure whether I'll get used to it.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
overrides: Update kernel source to 3.12.0-rc7.

... plus two more commits ;-)

Signed-off-by: aszlig <aszlig@redmoonstudios.org>