Add SELinux rules for service_manager.

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