add translations and internationalization features

This pull request adds all available French and Spanish translations to the site, as well as internationalization features for ease of browsing and language switching between available translations. 
- content is in /fr/ and /es/ respectively 
- content falls back to English content if no translation is available
- additional include files for language switcher element at the top of the right sidebar on sub-pages
- right side menu links get respective language codes appended to links in the CCK section.

Build & test using the add-translations branch.