Changes

Summary

1. clarified Mercurial version: presumably the last version that supports both python2 and python3;
2. more robust: avoid crash on non-Linux systems;
3. clarified webserver names;
4. proper Apache.php_name;
5. proper packages for mercurial_setup on Ubuntu 22.04: building from source provides hgweb modules, and also provides a defined version (6.1.1 is also provided by Ubuntu 22.04);
6. tuned source structure;
7. more robust systemd configuration;
8. more robust nginx configuration, notably for "certbot --nginx -d DOMAIN";
9. tuned whitespace in generated file;
10. tuned;
11. clarified modules;