Adds feedback to Home and Back tutorials.

Back feedback:
 - Too far from edge of screen
 - Cancelled (reversed gesture, swiped upwards, etc.)
 - Inside nav bar region
 - Demo: https://drive.google.com/open?id=1pc_hr7i-iZmgF37CN8oijPjhOvvsJoEG

Home feedback:
 - Too far from edge of screen
 - Paused too long (Overview detected)
 - Swiped sideways instead of up
 - Demo: https://drive.google.com/open?id=1NGYAlqV2wJtM2DOJ1pZM-r8N1SYVtMos

Bug: 148542211
Test: Manual
Change-Id: I627ed7c6e9b005d35794e4ae568529b5613cbf70