Use the Debian firmware package instead of the Intel-specific ones

The intel-*.nix modules are obsolete (since you can just say
‘hardware.enableAllFirmware = true’, or equivalently,
‘hardware.firmware = [ pkgs.firmwareLinuxNonfree ]’).  But we'll keep
them around for compatibility.
Update the locate database using a systemd service

This makes it easier to update the database manually ("systemctl start
update-locatedb").

Also, use modern module syntax.
Add /media and /run to the filesystems ignored by updatedb
Use the Debian firmware package in more places
Enable the Debian firmware package on the installation CD

It's unfree but we already had such firmware on the CD so we're not
worse off.

Issue #87.
not-detected.nix: Enable all firmware

Note that since the configuration produced by nixos-hardware-scan
includes not-detected.nix, you get all firmware when following the
regular installation procedure.

Issue #87.
Typo
try to fix zfs into initrd