Voice Interaction from within an Activity

This allows an app to show a voice search button
and invoke a voice interaction session for use
within the activity. Once the activity exits, the
session is stopped.

Test application has a new activity that
demonstrates it with the test voice interaction
service.

This initial version is functional enough for
an integration test, with some more tests
and improvements to come later.

Bug: 22791070
Change-Id: Ib1e5bc8cae1fde40570c999b9cf4bb29efe4916d