Update group editor styles and avatars for dogfood

* Use standard action bar w/ done button placement
  matching that on the contact editor
* Replace group member QuickContactBadge avatar with
  letter tile to match avatars in the main contacts
  lists. Also put it on the left side.
* Make the name in each group member row clickable.
* Don't use a two panel screen in landscape any more.

Bug 18641067

Change-Id: Id45a6ceb0a138906078356fa71a72225add07ecf