[PoC] Pricing configuration

Add validate pricing calculator configuration. This to prevent failure when we change calculator type.
@pjedrzejewski  I'll squash commits if you are agree.

Note: Forgot create new branch, There are two files not associated with this PR.
  - src/Sylius/Bundle/ResourceBundle/Controller/Configuration.php
  - src/Sylius/Bundle/ResourceBundle/Controller/RedirectHandler.php
This is wrong, you can't use function call in `empty()`, it will die with fatal error.

You would need to make code more like:
```php
if (!is_array($range) {
    return false;
}

$diff = array_diff(array_keys($range), array('min', 'max', 'price'));

return !empty($diff);
```

Which still is quite unreadable IMO.