Add attribute validator

[marcelsud]

Implement attribute validator for objects, such as:

class Customer
{
    public $name;
    public $email;
    public $address;
}

class Address
{
    public $street;
    public $number;
}

$customer = new Customer();
$customer->name = "John Doe";
$customer->email = "[email protected]";
$customer->address = new Address();
$customer->address->street = "Lorem ipsum dolor";
$customer->address->number= 123;

$customerValidator = v::attr("name", v::string()->minLength(5));
$customerValidator->attr("email", v::email());
$customerValidator->attr("address", v::attr("street", v::string())->attr("number", v::int()));

$customerValidator->validate($customer); //true