…orAggregate::getIterator PhpStorm support (Haehnchen)

This PR was merged into the 2.7 branch.

Discussion
----------

add docblock type elements to support newly added IteratorAggregate::getIterator PhpStorm support

| Q             | A
| ------------- | ---
| Branch       | 2.7
| Bug fix      | no
| New feature  | no
| BC breaks    | no
| Deprecations | no
| Tests pass   | yes
| License       | MIT

In additional to #16965 PhpStorm supports `IteratorAggregate::getIterator` now. see https://blog.jetbrains.com/phpstorm/2016/06/phpstorm-2016-2-eap-162-844/

example
```
$collection  = new \Symfony\Component\Routing\RouteCollection();
foreach ($collection as $route) {
    $route->getHost();
}
```

Commits
-------

ede3556 add docblock type elements to support newly added IteratorAggregate::getIterator PhpStorm support

I was just "playing" with the cart. stacking class together as i noticed collections do not provide ide support. This is just a example for one collection to support autocompletion.

So also how this was implemented in Symfony: symfony/symfony#19036

```
        $cart = new \Shopware\Core\Checkout\Cart\Cart();

        $cart->getLineItems()[0]->getDescription();
        foreach ($cart->getLineItems() as $item) {
            $item->getDescription();
        }
```

I was just "playing" with the cart. stacking class together as i noticed collections do not provide ide support. This is just a example for one collection to support autocompletion.

So also how this was implemented in Symfony: symfony/symfony#19036

```
        $cart = new \Shopware\Core\Checkout\Cart\Cart();

        $cart->getLineItems()[0]->getDescription();
        foreach ($cart->getLineItems() as $item) {
            $item->getDescription();
        }
```

fixes #18

I was just "playing" with the cart. stacking class together as i noticed collections do not provide ide support. This is just a example for one collection to support autocompletion.

So also how this was implemented in Symfony: symfony/symfony#19036

```
        $cart = new \Shopware\Core\Checkout\Cart\Cart();

        $cart->getLineItems()[0]->getDescription();
        foreach ($cart->getLineItems() as $item) {
            $item->getDescription();
        }
```

fixes #18