Ported i18n javascript to WET 4.0

- all language functions were kept save the .ago() from the WET 3.1 PE object. This was not leveraged by the web feeds plugin from what I can tell anymore since it has been upgraded to the twitter api v.2.0 which does the heavy lifting now.
- Bound the i18n object to the window object to allow for easy access for developers using the plugin template
- Leveraged document.documentElement.lang property for localization detection in vapour
- How to use : i18n(key,state,mixing) -- i18n("%top-of-page") outputs -> "Top of Page" in the document's set language