Add method Phalcon\Mvc\Collection::getColumnMap/setColumnMap

```php
class Users extends \Phalcon\Mvc\Collection {
	public function initialize()
	{
		$this->setColumnMap(array(
			'_id' => 'id',
			'fullname' => 'FullName',
			'email' => 'Email',
		));
	}
}
```