Add required meta data

[hirnschmalz]

Regarding the Unsplash API Guidlines a link back to unsplash and the user of the image must be set.

When displaying a photo from Unsplash, your application must attribute Unsplash, the Unsplash photographer, and contain a link back to their Unsplash profile. All links back to Unsplash should use utm parameters in the ?utm_source=your_app_name&utm_medium=referral

To be able to do so the required information must be saved in TYPO3s sys_file_metadata.

Any plans to implement this in the near future?