[request] embedded internationalization (i18n)

[puzrin]

I'm hot sure how to post request right, so posting to issue, according to template. Correct me, if i do something wrong.

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No i18n (gettext), suitable for embedded use

Existing i18n crates have heavy extra dependency, ok for desktop, but not suitable for restricted embedded requirements.

Also, gettext prefer use PO-files, but yaml (like in ruby's i18n) is more human-friendly.

Success Criteria

Create a set of tool + runtime to translate texts the same way as gettext.

• Phrase scanner - creates YAML files, to be translated by humans,
  • optionally, for import/export to web translation services
• "Renamer" - if source phrase changed and you need to update key in all translations
• Compiler - take YAML files and build rust code

Work in progress

• lv_i18n - i did tool with node.js for C. This may look strange, but is has verified workflow, data structures and API features set. Now it's possible to skip top level architecture design and just implement similar thing in Rust.