User experience studies and recommendations for providing an option to change language

See https://gitlab.com/agaric/sites/agaric-com/issues/160

@later tell Gnuget OK i think the thing that was ‘breaking’, that was really making it difficult for me to continue styling the feed, was after the translation stuff was working, it caused the existing condition on the taxonomy term view (including feeds) - “Content: Translation language (= Content language selected for page)” - to make nothing show up. Maybe worth another blog post? Taxonomy term listings and feeds should be multilingual by default for sites doing ‘best effort’ translation, but the default configuration assumes complete translation basically?