Make PaginatedResourceCollection usable without Resource object

[mdumoulin]

Reason for this PR

This PR makes PaginatedResourceCollection usable without dedicated Resource object. In such case, You will get a list of HalResource.

$apiHost = 'https://api.shopping-feed.com';
$storeId  = 99999;
$token    = '...';

$options = new Client\ClientOptions();
$options->setBaseUri($apiHost);
$options->setHttpAdapter(new Http\Adapter\GuzzleHTTPAdapter($options));

$client = new Hal\HalClient($options->getBaseUri(), $options->getHttpAdapter());
$client = $client->withToken($token);

$resource = $client->request('GET', "/v1/store/$storeId/order", ['query' => ['limit' => 10]]);

$iterator = new PaginatedResourceIterator(
    new PaginatedResourceCollection($resource)
);

$orders = [];

foreach ($iterator as $order) {
    $orders[] = $order->getProperty('id');
}