Add animations to RecyclerView

This CL adds the basic plumbing for animating item changes in
RecyclerView. It also implements the bare essentials add/delete
animations. When the app specifies that items have been
added/removed (by calling the appropriate Adapter methods), the
RecyclerView will determine the appropriate fading and moving
animations to animate the items being added, removed, and moved
into new locations.

Change-Id: If70c09e7af168ce5963c785b5886a18c87a7dc98
9 files changed