Atlases' languages should be configurable via the nunaliit executable

[alexgao1]

Language configuration could be updated with nunaliit update instead of dealing with it in the code.
It should:

• be a configurable file that contains an array of languages
• have a language marked as a default

Example of what the file might contain:

[
    { code: "fr", name: "French", isDefault: true },
    { code: "en", name:" English" }
]