Toggle option for embedded objects displaying as in-line previews or attached-files#305

A general toggle option (maybe in the corner) on each embedded picture/files/link object to switch between displaying as an attached-file, or to attempt an in-line preview

By attached-file view, I mean what is currently done for PDFs, etc.
By in-line preview, I mean what is currently done for pictures and youtube links

For example:
Pictures by default should continue to display the image in-line (but should be able to convert to just an attached-file)
PDFs could default to attached-file as is, but eventually maybe an option to show an embedded in-line preview of the first page as an image
Youtube videos should continue to default to displaying the video in-line but should be able to convert it back to a link
Other video file types (if ever supported in the editor), could have an option to switch between displaying as attached-file or an in-line preview