Improve ergonomic design of instance card tooltips.

[atrieder]

Depending on the web browser being used (i.e., Google Chrome), activating a tooltip for an instance card on a grid page will cause the tooltip to expand in-place, shifting the surrounding elements upwards. So far, the following undesirable results have been observed:

• When only one row of cards can be displayed on screen, the entire website appears to shift upwards.
• When there is more than one row of visible cards, the tooltip will either cause the current row to shift upwards or the next row to shift downwards (The former may be observed in Safari and the latter may be observed in Google Chrome).

The above results would be especially noticeable as more instances are incorporated.

A potential replacement design for the tooltip may be the following: Rather than expanding the size of the card below the thumbnail image, the thumbnail image itself may slide upwards "within" the boundaries of the card (that is, the portion of the thumbnail that is outside of the card border will be effectively hidden from view) as though it were a drawer covering the tooltip in the z-axis. The tooltip's contents would remain in a fixed position, so the overall size of the card would remain constant at all times.

[atrieder]

With the latest commit, we now have tooltips that appear in the place of their corresponding cards (they do not expand or otherwise shift the surrounding elements). So, I think that this issue can be closed.