Cleanup of the PackageInstaller API - PackageInstaller

The PackageInstaller app manages side-loading apps as well
as permission management. It should be updatable, hence
should rely on system APIs to talk to the platform. This
is the first step of defining an API boundary.

Change-Id: I37aea1e5cc3195b8b636af6790af45fe5a9765cd
27 files changed