This attempts to display the tooltip to the left of the current asset, but Popper.js is smart enough not to fix it there if that would keep it offscreen. 

There’s just enough CSS to add a border — this could probably use some additional TLC for more distinct colors and we probably want to adjust widths and font sizes, too.

See #998

This avoids overlapping the thumbnail where possible

Since the tooltip no longer fills the element with the metadata display, which makes it less obvious which asset is being displayed. This adds a hover outline similar to the active asset color to make those states more distinct.