Embed full documentation in releases

[opensemanticsearch]

Since there is not only fulltext search but more and more features, we have to export the documentation from (Drupal powered) website to local HTML files.

So in future by clicking "Help" you can access the full documentation (at the moment only the very short help text) offline or within your intranet, without accessing a public website.

[Mandalka]

Downloaded quick and dirty by

wget --mirror --convert-links --html-extension --page-requisites --no-parent http://opensemanticsearch.local/doc/

so you collaboration and improves of the documentation by pull requests are possible in new repository https://github.com/opensemanticsearch/open-semantic-search-doc

[Mandalka]

Done by #392