Localisable metadata

[edsilv]

Allow setting locale in the info.yml, e.g.

-   - en
           label: The Lord of the Rings
    - de
           Etikette: Die Herr der Ringe
-   - en 
           description: The Lord of the Rings Trilogy
    - de
           Beschreibung: Die Herr der Ringe-Trilogie

[edsilv]

Could be more manageable to break into separate yml files then merge on build? e.g.

info.en.yml
info.de.yml

[edsilv]

Default language is now @none as per IIIF presentation 3.