Incorporate NixOS configuration

TL;DR:
- Move /etc/nixos/configuration.nix -> //nixos/configuration.nix
- Move /etc/nixos/hardware-configuration.nix -> //nixos/harware.nix
- Document installer.nix
- Create rebuild.nix wrapper around `sudo nixos-rebuild switch`

Previously I sketched ideas for the configuration.nix for socrates -- also known
as flattop -- the inexpensive Acer laptop residing in my flat and stored that
configuration.nix file in briefcase. Now, however, I have successfully installed
NixOS onto socrates. By default NixOS saves the configuration.nix and
hardware-configuration.nix files to /etc/nixos/. I'm moving both of these files
into briefcase.

Because the command `nixos-rebuild` looks for the NixOS configuration
file in /etc/nixos, I wrote rebuild.nix, which creates a program to
call `nixos-rebuild` with the new location of my configuration.nix.

1 files changed, 1 insertions, 0 deletions

diff --git a/nixos/installer.nix b/nixos/installer.nix
index f0c1efe21ef5..276b1f60df49 100644
--- a/nixos/installer.nix
+++ b/nixos/installer.nix
@@ -1,3 +1,4 @@
+# This expression can be used to create NixOS .iso images.
 { config, pkgs, ...  }:
 
 {