Allow specifying more options per endpoint (e.g. access callback)

For example:

```php
protected $controllers = array(
  '' => array(
    // Shorthand.
    \RestfulInterface::GET => 'getList',
  ),
  '\d+' => array(
    // Verbose
    \RestfulInterface::GET => array(
      'method'=> 'viewEntity',
      'access callback' => array($this, 'accessViewEntity'),
    ),
  ),
);
```

So the access could be moved to it's own method per endpoint.
GET => HEAD