Improved French pages

* On mailing_lists.fr.html, fix the "en" link that didn't work on Chrome
* On support.fr.html, fix the table of consortium members, and link directly
   to mailing_lists.fr.html.
Merge pull request #406 from lefessan/community-french

Improved French pages
Improved install.fr.md page

* Fix latest version
* Translate OPAM usage
Merge pull request #407 from lefessan/install-french

Improved install.fr.md page
Improve French version of mailing_lists.md
The first page in French
Add alt tags on images
Improve index.fr.md baseline
Add a script to translate navbar.mpp
Merge Lefessan's contributions to the French Mailing List page
Add translation "buttons" to the front (core) page
Improve translation script

* Remove "open Printf", which decreases the readability of code
* Remove useless function "language_of_ISO639"
Merge branch 'master' into index.fr.md
Fix to use standard translation links
Fix Tutorials.Modules (fr) header overlaying breadcrumbs and lang selector

Apparently ---- underlining in markdown creates an H2 header which has different styling in bootstrap_mod.css than an H1 header such that the header box ends up catching most clicks on the breadcrumb or language selector links.
Fix Tutorials.Structure (ja) header overlaying breadcrumbs and lang selector

Same as #415
Fix Tutorials.Set (ja) header overlaying breadcrumbs and lang selector

Same as #415
Fix Tutorials.Map (ja) header overlaying breadcrumbs and lang selector
Fix Tutorials.Streams (en) header overlaying breadcrumbs and lang selector
Small improvements to the French front page