TYPO3 Core

While hardening the ImageService it was restricted to core's FileReference instead of also allowing extbase FileReferences - the code for converting them is still there but not reachable anymore due to the restrictive type hint.

To test:

- Create an '\TYPO3\CMS\Extbase\Domain\Model\FileReference' and call ImageService::getImage('', $image...)

Easy core steps:
- Use the form framework to create a form with an image upload field.
- Add a summary page to the form
- Use the form in frontend and upload an image - get the error when looking at the summary
[note: after applying the patch you will get a second error because of changed meta data handling, however that's a separate issue]