Possible fix for #80.

* Added ajax_csrf_token.js that uses the jQuery ajaxPrefilter method to
add the csrf_basic key found in the body tag to all ajax requests done
to (www.)hackthis.co.uk.
* Added ajax_csrf_token.js to the default loaded js files for logged in
users.
* Added a check for the csrf key to the ajax/forum.php file. This, if
found to be working, should be extended to all ajax handle files.