Rename ranker to assistant and make some of the methods public.
Delete the ext services ranker and restore the listener-type
lifecycle to the assistant.
Test: manual. add a notification assistant and verify it gets
assistant and listener callbacks.
Change-Id: Ia3406c8c14d923426c1b8a6d8b5187efe64c31c3
The services library will contain platform components that we want
partners to not customize or ones we want to update faster than the
platform.
The shared library will contain code that we commit to be available
on the device which apps can load if they so desire.
bug:25450378
Change-Id: Iaebb68129a13af9e03e25ea198764d382ad49404
