Add encrypted attribute modifier

[daftspunk]

Related issue:
rainlab/mailchimp-plugin#1

In the same family as hashable, purgeable and jsonable; another type is needed for storing sensitive data in the database encrypted.

This should be added to October's ActiveRecord model.

class User extends \October\Rain\Database\Model
{
    protected $hashable = ['password'];

    protected $purgeable = ['password_confirmation'];

    protected $jsonable = ['permissions'];

    protected $encrypted = ['api_key']; // <== New
}

• $encrypted - values are encrypted and decrypted for storing sensitive data.

[daftspunk]

This is implemented with the Encryptable trait