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

Created by: el00ruobuob

This is a POC of translation optilization as discussed in #725 (closed) 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.