* Fix the FW names
FW_REFUSE was removed and nixos-fw-input was renamed to nixos-fw.
* Update the comment (documentation) at the top
Order the chains of the main table alphabetically (like in the rest of
the file) and add nixos-fw-rpfilter (from the raw table) and nixos-drop
(used while reloading the firewall).
* Refactor the module (mainly comments)
- Move some attributes to the top for better visibility (that should
hopefully make it easier to read and understand this module without
jumping around too much).
- Add some missing examples and improve some descriptions.
- Reorder the mkOption attributes for consistency.
- Wrap lines at 72 characters.
- Use two spaces between sentences.