Initial Binder interface for installd.

Define an AIDL for installd, starting with a single method.  Publish
that interface for the system to start using.  We'll circle back and
migrate more methods in future CLs.

Migrating installd to Binder will allow us to get rid of one of
the few lingering text-based command protocols, improving system
maintainability and security.

Test: builds, boots
Bug: 13758960, 30944031
Change-Id: Icdb5320082567e0355d8f76f413f01cfacf0fb99