Implement issue #3221502: New APIs to support new back stack / task navigation

What this adds:

- A new Intent activity flag to completely replace an existing task.
- A new Intent activity flag to bring the current home task up behind
  a new task being started/brought to the foreground.
- New versions of startActivity() that take an array of Intents to be
  started, allowing applications to start a task in a specific state.
- A public moveTaskToFront() method on ActivityManager, with a new flag
  that allows the caller to have the task moved to the front with the
  current home task immediately behind it.

Change-Id: Ie8028d09acffb5349d98043c67676daba09f75c8
22 files changed