Internationalization

[julienmalik]

Fixes #13

It generates index.$lang.html for all langs if you put something like :

multilingual: 
  - fr
  - es

in the root settings.yaml

The first defined language is special :

• it is default one (if browser locale is not in available locale, this is the fallback)
• it generates index.html, not index.$lang.html so that we always have an index.html (without the need to symlink/configure webserver/...)

To be multilingual, the gallery .yaml text sections then needs to be like :

title:
    fr: Salut
    es: Ola

but the monolingual case is still supported as before.
when generating a multilingual version, if a string is not translated (title: Hello) then it is used for all languages.

multi langages are supported only for title, subtitle and text keys.

On the html side, each page embeds a small javascript snippet which tries to redirect to the browser-locale version if it is available (and falls back to the default locale).

Didn't test static pages yet...
For the rest, it fulfills my needs for the moment so I'll stop here, waiting for comments.

[julienmalik]

cc @abeudin

[julienmalik]

doesn't work for menu (yet)

[julienmalik]

now it works for menus too with :

menu:
  - about:
      en : "About"
      fr : "A propos"
  - first_gallery:
      en : "My first gallery"
      fr : "Ma première gallerie"
  - http://twitter.com:
      en : "Twitter"
      fr : "Touitteur"