Add screen for turning TalkBack on and off and remove intent to launch TB

tutorial from SUW. Also fix how Fragments are displayed (Fragment Views
were being inflated incorrectly causing bugs like the one where TB would
still see the hub elements on child screens) and  remove ripple from 
non-selectable text.
Bug: 27203716
Bug: 27218687
Bug: 27066012
Bug: 27587193

Change-Id: I4c6724b3ff6d6a7fca3d0f419a5e1c82ee1071d5