Add all css edits to EXTRA.css

Note that with the introduction of 1.2, editing templates is now much easier to manage due to the built in merging functionality: http://xenforo.com/community/threads/template-merging-and-history.48846/

Whilst you can continue using EXTRA.css, editing templates is now an equally valid approach and won't necessarily introduce any additional work when it comes to upgrading.

See this resource for more information: http://xenforo.com/community/resources/a-guide-to-xenforo-1-2-and-templates.2115/