Fix PreferenceGroupAdapter highlight code path

- do not change the Preference View background. Instead wrap
the Preference View into a FrameLayout with the highlighting
Drawable as the background
- test the View type to force the Preference View creation and
not rely on the convert View when highlighting
- define a new View type for the highlighting
- increment getViewTypeCount() returned value (for the new type)

Change-Id: Ie5f19311e11545aba848fd637ec61e43071d8dcf