Update translations in locales directory

This pull-request adds a button to the workflow details view for automatically updating the translations in the locales directory of the corresponding package.

See the updated documentation in the readme for hints about how it works.
Adds a new dependency to ``i18ndude`` - which is then installed in production too..

~~The new feature does not change the `.pot`-files directly, but it creates a `-lawgiver.pot` which should then be merged. https://github.com/4teamwork/ftw.recipe.translations/pull/3 adds support for this to `bin/i18n-build`~~

@maethu @deiferni