Implement i18n folder-per-locale support

[spacechase0]

            helper.ConsoleCommands.Add("meow", "meow", (cmd, args) =>
            {
                foreach (var t in Helper.Translation.GetTranslations())
                {
                    Log.Info("translation:" + t.Key + " " + t.ToString());
                }
            });

[Pathoschild]

Merged into develop for the upcoming SMAPI 4.1.0, and documented on the wiki. Thanks for the help!