Merge: nitcorn server for nitiwiki

This PR contains the initial work of @ablondin and integrates it further with nitiwiki.

Intro a simple nitcorn server to publish the static files generated by nitiwiki and allow modifications from a web form. It is already applied on http://xymus.net/ to manage the main page.

The server reads the `config.ini` of the target to find the path to the public files. It writes the new markdown to the source folder and regenerates the wiki on each modification. The modification forms apply the template of the current wiki. (with some imperfections)

I've added a basic password authentication system using a list of hashed passwords in a simple text file. It should be enough for simple deployment of the server and this file can be ignored by git.

Limitations:
* Not integrated with all configuration of a nitiwiki server.
* Creating new files is supported by manually changing the path in the URI, but creating parent folders of a file is not supported.
* Some paths configuration may cause problems, the `edit/` page must be at the root of the server and other similar restrictions were not fully tested.
* There's no integration with git.

Closes #1832

Pull-Request: #1877
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Jean Privat <jean@pryen.org>