Add a service_mananger class with the verb add.
Add a type that groups the services for each of the
processes that is allowed to start services in service.te
and an attribute for all services controlled by the service
manager. Add the service_contexts file which maps service
name to target label.

Bug: 12909011
Change-Id: I017032a50bc90c57b536e80b972118016d340c7d

New property_contexts file for property selabel backend.
New property.te file with property type declarations.
New property_service security class and set permission.
Allow rules for setting properties.