[3.2][WIP][ticket/12769] Add CDN version of font-awesome for development

#### TODO:

- [ ] Add CDN version of Font-Awesome 4.1.0
- [ ] Replace all icons with fa best guess !placeholders
- [ ] Remove all icon images
- [ ] Remove all css rules related to applying the various icons
- [ ] Remove all the unnecessary HTML bits
- [ ] Cleanup the semantics in the HTML
- [ ] Cross browser checks
- [ ] Determine final choices for icons
- [ ] Fix any gap icons maybe we use [Fontastic](http://app.fontastic.me/#) implementation of fa + whatever else we need?

PR: https://tracker.phpbb.com/browse/PHPBB3-12769?jql=text%20~%20font%20ORDER%20BY%20created%20DESC

PHPBB3-12769