Fixed #17064 -- Improved the UX for the admin's time and date picker widgets...

Fixed #17064 -- Improved the UX for the admin's time and date picker widgets by brushing up the 'Cancel' button's visual feedback and by allowing the popups to get closed by pressing the 'Escape' key.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17021 bcc190cf-cafb-0310-a4f2-bffc1f526a37