Initial commit of InputManager and keyboard layout API.

Added a new InputManager service for interacting with input
devices and configuring them.  This will be the focus of
an upcoming refactoring.

Added an API for registering keyboard layouts with the system
based on the use of a broadcast receiver.  Applications can
register their own keyboard layouts simply by declaring a
broadcast receiver in their manifests.

Added the skeleton of a package that will ultimately contain
the keyboard layouts and other input device related resources
that are part of the base system.

Bug: 6110399
Change-Id: Ie01b0ef4adbd5198f6f012e73964bdef3c51805c