Add new fade in/out feature for drawable containers.

This is used to allow list view's pressed and activated indicators
to fade in an out, though of course it can be used elsewhere as well.

There is a lot of complexity in supporting this in list view.  The
two main things that are being dealt with:

- When recycling views, we need to make sure that the view's drawable
  state doesn't get animated from an old row's state.  The recycler
  now keeps track of which position a view was last in, and if it is
  reused at a new position there is a new View/Drawable API to tell
  it to jump to its current state instead of animating.

- For the pressed indicator to fade out, we need to keep displaying it
  after it is hidden.  There are new variables and code to keep track
  of this state, and tweaks in various places to be able to remember
  the last selected position and continue updating the drawable bounds
  as needed.

Change-Id: Ic96aa1a3c05e519665abf3098892ff2cc4f0ef2f