Initial implementation of new voice interaction API.

This gives a basic working implementation of a persist
running service that can start a voice interaction when
it wants, with the target activity(s) able to go through
the protocol to interact with it.  It may even work when
the screen is off by putting the activity manager in the
correct state to act like the screen is on.

Includes a sample app that is a voice interation service
and also has an activity it can launch.

Now that I have this initial implementation, I think I
want to rework some aspects of the API.

Change-Id: I7646d0af8fb4ac768c63a18fe3de43f8091f60e9