Gherkin Language Features: - Internationalisation

[alistairjevans]

We need to support multiple languages from the perspective of the fixed keywords, e.g. Scenario, Feature, and so on.

Different token types will require changes to the lexer; it would be good to not have to rebuild the entire parser each time, but we could have multiple lexers (one per language).

Perhaps we could split the lexer tokens file into a file that is always fixed, and one that can vary.

Bonus points if it's extensible, so a library can add a lexer that supports a different language.