Localization

[Maselkov]

I've never done any l10n before, and especially not for this type of app, but this is the rough outline that I figured so far. Any help is appreciated.

• [x] Figure out the best way to wrestle gettext or equivalent into submission in this use case. Gettext seems to only really care about the system's locale, when in this case, it's the locale of the Interaction that we care about. Some wrapper around gettext perhaps, or something entirely custom? Maybe there's libraries for that? Need to research
• [ ] Mark the necessary strings as translateable once a function is figured out with _()
• [ ] Extract them with pybabel
• [ ] Put the files up for translation, source the translations