Update nav.php to use relative path hyperlinks

[akbaig]

This pull request removes the dependency of placing the project at the root level of a website.

1. Nav.php uses relative path for the hyperlinks
2. Hyperlink paths are adjusted dynamically (depending upon where the module is called from, /index.php or logs/index.php)

Example:

www.website.com/something/index.php ✅ (Relative hyperlinks still work in this case)

@MichaelBelgium