[POC] DO NOT MERGE - proof of concept of translation optimization

[el00ruobuob]

This is a POC of translation optilization as discussed in #725
The download page is changed using the usual yml file, a generic html file, and a md file which only includes the HTML along with the snippet for untranslated pages.

@rehrar, please have a look on my publicly available local build on which you know how to connect.

[el00ruobuob]

Adding the french translation in yml, to be sure it is multilingual.

[rehrar]

Yes, I'm making this as we speak for all languages and it's working fine. :)

[el00ruobuob]

Great! I wonder if we should add a

translated: yes / no / partially

Statement and use it with a {% if ... elseif ... %} to display the message, even a different message for partial translation, and moreover tell the world not to touch those files, and only change the yml.

[el00ruobuob]

As @rehrar is already working on the exact same stuff, i'm closing it.
All discussions may be done in #725