launch_daemon: Added basic logging facility

* The daemon now stores many events in am internal log.
* You can use "launch_roster log" to retrieve it.

launch_roster: Added restart, start/stop works on targets.

* If the launch_daemon returns B_NAME_NOT_FOUND for a job, it'll
retry the same name as target.

launch_daemon: Added ability to enable/disable a job.

* Instead of just starting/stopping it.
* Also available via the launch_roster command.

launch_roster: The beginnings of a launch_daemon control tool.