LoadTranslations loads translation files. getLanguageFn should return a language
string (e.g. 'en-US'). If getLanguageFn is nil, then the loadSystemLanguage function
is used, which uses the 'LANG' environment variable.
T translates a string, possibly substituting arguments into it along
the way. If len(args) is > 0, args1 is assumed to be the plural value
and plural translation is used.