PackageManager: Add optional prelaunch check step

This ability is protected by config overlays.

Change-Id: I0c80bd9ec6bda3d21557aaa9503f05ff86adf434
Add system|signature permission for intercepting package launch.

The preLaunchCheck (add, remove) functions which allows an application to
perform any checks before the framework launches the app
needs to be a protected with a system|signature permission.
This change defines the permission and protects the functions with it.

Change-Id: Ib62e25b780df39c4a7d9d1e4eaf3fc98ffa4089c

Conflicts:
	core/res/AndroidManifest.xml
	core/res/res/values/cm_strings.xml