Added Categories ("tags" on the website)

* Added definition SITE_CATEGORIES() with all "tags" on the website
* Added a Categories dir in the CATEGORIES() definition
* Changed the INDEX() definition to incorporate the "tags"
* Changed the INDEX() definition to add page browsing (+ limited pages)
* Changed mode argument from integer to string (more clear what option
you want)
* Added an extra mode (getSiteCategories) to incorporate the new "tags"
Version 1.0.1