Image/video icons should only be visible during hover

[pjcross]

I think that there is some confusion on how this should work. My intent is that we should only make the icons visible while the user is interacting with a particular image during hover. The rest of the time, the icons should be invisible so that they are not blocking visibility for sections of the image (preserving our screen real estate for the image content). When the mouse moves over an image, then all 3 icons should be shown and should be functional.