Add zfs module.
Need extraModulePackages for spl and zfs modules.
Add the hostid option. Refactor code a bit better for initrd(untested) and system operation.
spl module params in boot.spl.*
Support driSupport32Bit for nvidia legacy 304.

I need this for steam to work with some older cards.
Merge remote-tracking branch 'upstream/master'
Maintain iso_efi
gummiboot-builder: When NIXOS_INSTALL_GRUB is set and efibootmgr is used, prepend the gummiboot entry to the boot entries list
gummiboot-builder: Only read /etc/machine-id once per invocation
etc.nix: Fix style
Turn environment.etc into an attribute set

This provides a more convenient syntax and allows easier overriding.

For example,

  environment.etc = singleton
    { target = "vconsole.conf";
      source = vconsoleConf;
    };

can now be written as

  environment.etc."vconsole.conf".source = vconsoleConf;
environment.etc: Add convenience option 'text'

This allows writing

  environment.etc.hosts.text = "127.0.0.1 localhost";

instead of

  environment.etc.hosts.source = pkgs.writeText "hosts" "127.0.0.1 localhost";
Selectively allow /etc files to be disabled

For instance, if you don't want NixOS to emit /etc/hosts, you
can say:

  environment.etc.hosts.enable = false;
nixos-install: Respect host $NIX_CONF_DIR and don't assume nix.conf exists
nixos-install: Respect /home/shlevy/src:/nix/var/nix/profiles/per-user/root/channels/nixos:nixpkgs=/etc/nixos/nixpkgs:nixos=/etc/nixos/nixos:nixos-config=/etc/nixos/configuration.nix:services=/etc/nixos/services to find the nixos and nixpkgs sources, only copy the nixos channel if it exists
nixos-install: Respect the build-users-group of the host
nixos-install: If NIX_CONF_DIR is unset, use /etc/nix
nixos-install: Don't grep nix.conf directly, use nix perl bindings instead
Use nss_myhostname from systemd
D'oh