- Changed helper and language autoload

- Changed language config
- Removed never used constants
- Changed rest_language in rest config file
- Adapted models that where extending FHC_Model
- Adapted code to load hlp_return_object
- Adapted code to use exit status codes constants

application/config/rest.php

@@ -516,4 +516,4 @@ $config['rest_ajax_only'] = FALSE;
 | Language file to load from the language directory
 |
 */
-$config['rest_language'] = 'en-US';
+$config['rest_language'] = 'english';