Polish the details of the tab grid presentation/dismissal animation, including:

- Overall timing
- Timing of staggered events 
- Animation curves
- Aspect ratio on active cell should start matching the open tab, and then transition to match the grid cell.
- The active tab should transition out with something better than an alpha fade.
- The tab grid controls drop in too soon.
 

Add custom motion animation when tabs in the tab grid rearrange.

Tabs should move along curved paths, not linearly, and the overall motion should be staggered so the tabs don't all move in unison.