Internationalization

[fxbenard]

Creation :

• languages folder,
  -default.po files
• and the french translations

[alexkingorg]

Hmm, I'm not sure how I feel about adding localizations to this repo. I guess it would be good to support them.

The actual format strings for the tabs are coming from the WP taxonomy data. Is that localized already in WP core?

[fxbenard]

It is : standard, en passant, lien, citation, image, galerie in french, everything is translated except your 8 strings, it's a little odd but it's up to you. I didn't figure out how to make my translation work with your translate function, i'm used to the textdomain one.
If you don't want to use it keep it aside for when you feel like using it