Don't mount /nix/store ro if it's a mountpoint

In principle this could work, but the current remount logic in nix fails
to remount mountpoints that are root in their own filesystem (as would
be the case with bind-mounting a mountpoint over itself). nixos/nix#98
is aimed at fixing this.

Signed-off-by: Shea Levy <shea@shealevy.com>
Add Transmission BitTorrent service

Enable it with

  services.transmission.enable = true;

and optionally configure it

  services.transmission.settings =
    {
      download-dir = "/srv/torrents/";
      incomplete-dir = "/srv/torrents/.incomplete/";
      incomplete-dir-enabled = true;
      rpc-whitelist = "127.0.0.1,192.168.*.*";
      # for users in group "transmission" to have access to torrents
      umask = 2;
    };

The above settings are written/merged into settings.json each time the
service is about to start.
Merge pull request #110 from bjornfor/transmission-service

Add Transmission BitTorrent service
xfce: update the xinitrc path
Console key map: Make option uniq

Signed-off-by: Shea Levy <shea@shealevy.com>
smartd: change 'devices' option from "list of strings" to "list of attribute sets"

The smartd used to expect a list of devices to monitor. After this patch, it
expects a list of attribute sets, which may have two attributes:

 - device: path to the device (required)
 - options: smartd options to apply to this particular device (optional)

A concrete example configuration would be:

  services.smartd = {
    enable = true;
    devices = [ { device = "/dev/sda"; } { device = "/dev/sdb"; options = "-d sat"; } ];
  };

Furthermore, the config option 'deviceOpts' can be used to configure options
that are applied to *every* device.
need a newline in extraModprobeConfig
Merge pull request #119 from jcumming/zfs.130311

need a newline in extraModprobeConfig