Various fixes and improvements to window, activity.

- New meta-data you can add to a dock activity to have it launched by the
  home key when the device is in that dock.

- Fix a deadlock involving ActivityThread's internal content provider lock.

- New window flag to have a non-secure keyguard entirely dismissed when a
  window is displayed.

- New WindowManagerPolicy APIs to allow the policy to tell the system when
  a change it makes during layout may cause the wall paper or
  overall configuration to change.

- Fix a bug where an application token removed while one of its windows is
  animating could cause the animating window to get stuck on screen.

Change-Id: I6d33fd39edd796bb9bdfd9dd7e077b84ca62ea08