Need functionality to disable automatic CSRF checking

[kenjis]

If we enable automatic CSRF checking, all REST calls will fail, unless they contain a token, which is not likely.

See https://github.com/fuel/core/pull/1974#issuecomment-183992069

How to implement it?

[kenjis]

CodeIgniter's implementation:

$config['csrf_exclude_uris'] = array('api/person/add');

$config['csrf_exclude_uris'] = array(
        'api/record/[0-9]+',
        'api/title/[a-z]+'
);

https://www.codeigniter.com/user_guide/libraries/security.html#cross-site-request-forgery-csrf