Integration of a new Documentation

The following manual steps are necessary for each added documentation:

1. Create a subfolder with the name of the release identifier (e.g., master, v2.0)
2. Copy contents of Doxygen html folder into directory
3. Add documentation meta data to docs/docs.pug
4. Adjust the sort order of the documentations array in the config file; the order is used for display
5. Adjust doxy-boot.js
   1. Add code to generate backlink in the $(document).ready callback

The resulting head of the file should look like this:

$( document ).ready(function() {
    $("#projectlogo").each(function() {
        var td = $(this);
        td.html($("<a>").attr("href", "/").append(td.html()));
    });
    
    // ...
});