Migrate "Internationalisation for Developers" to Dev Guide

Created by: seancolsen

This wiki page on Internationalisation for Developers is currently outside the scope of the Dev Guide migration, but I think it belongs in the Dev Guide. Does this make sense to you @mlutfy ? My logic here is that most developers are not likely to go looking into the i18n resources unless they're specifically interested in translation, whereas this page offers important info for people who are not actually do any translation.