Inject ResourceEvent with Request object

A common feature request I've heard in IRC as well as the mailing list is for the ability to access the request object within a REST resource. In the current implementation, this is impossible, and requires that you push any additional data you want from the request into the resource via "event parameters" (`$resource->setEventParams(...)`). 

This patch implements logic to compose a Request object in the ResourceEvent, and a workflow in the RestController for injecting the Request into the Resource as an event parameter so that it will be pushed into the ResourceEvent when created. This allows full access to the Request object within service resource listeners.

This will likely address zfcampus/zf-content-negotiation#13 as the reporter of that issue would be able to execute the following to retrieve the requested language:

```php
$request = $this->getEvent()->getRequest();
$headers = $request->getHeaders();
$lang    = 'en';
if ($headers->has('Accept-Language')) {
    $header = $headers->get('Accept-Language');
    foreach ($headers->getPrioritized() as $language) {
        if (! in_array($language, $knownLanguages)) {
            continue;
        }
        $lang = $language;
        break;
    }
}
```