Increase ease of adding additional files/links to video objects

[and]

Many videos would benefit from having additional media associated with them (audio, pdfs, images, text etc.) It would be great if Plumi made it easy to add these items easily with the video object as few users will use the Plone system of creating a new folder, adding items into it, and then linking them back in kupu.

Exactly what is needed here still remains to be specced out, that's the first step.