Various performance and other work.

- IME service now switches between visible and perceptible depending on
  whether it is being showm, allowing us to more aggressively free its
  memory when not shown.

- The activity display time is no longer delayed by the activity
  transition animation.

- New -R (repeat) option for launching activities with the am command.

- Improved some documentation on Loader to be clear about some methods
  that apps should not normally call.

- FrameworkPerf test now allows you to select individual tests to run.

Change-Id: Id1f73de66dc93d63212183958a72119ad174318b