Sandbox changes for use in UXR prototype.

 - "All Set" screen doesn't show after Home/Overview/Back tutorials.
 - X button in top left is hidden (we'll want to move this to the
   feedback view).
 - Feedback pops in and out from the top of the screen.
 - Hand animation is replaced by video feedback at start and after
   incorrect gesture.
 - Back tutorial goes left then right, in order to match video.
 - Updated strings and marked translatable (UX-reviewed already).
 - Added Chinese translations.
 - Many other things.

Test: Manual
Change-Id: I126a3ea0dad645014fab9cdee2ed19e06a8a56e9