Configuration in NixOS

Configuration in NixOS is not very straightforward. On other Linux
distribution site-specific information (password files, host files, and
so on) are stored with information that is rather generic for a lot of
operating systems. To be able to handle these in a gentle way I have decided
to seperate these two a bit more in NixOS.

In particular, in the /etc directory there is a Nix profile called "configs".
In this profile the generic configuration is kept. In time this can grow
to keep configuration which is site specific, but which can easily be kept
in the store, such as "profile" (default system wide Bourne shell profile)

Right now two packages should be in this profile:

* etcServices : installs a file called "services" (/etc/services should
point to this)
* etcProtocols : installs a file called "protocols" (/etc/protocols should
point to this)

During install time these packages should be installed and the right symlinks
should be made.

When NIX-40 is closed, we might consider making /etc itself a profile and
keep even more configuration information inside the Nix store.