Implemented service.start (with dummy exec implementation)

In addition to the command, I fixed a whole bunch of logic in the service state machine,
and an incorrect assumption that I didn't need to trap SIGCHLD.

The service state machine now goes full circle through starting, up, reaped, and down,
and all that is left for a bare-bones process supervisor is exec() and parsing of service
metadata for the auto-restart flag.  (and a shutdown sequence)