allow parameters for restart effector, including children and the machine for SoftwareProcess.restart;

if this model is sensible i'd like to apply it more widely to effectors, to allow parameters to tune behaviour.
(eg for stop, to allow controlling whether it is the machine or just the process which is stopped,
and on start, to allow forcing reinstall)
Should `{@link #START}` actually be `STOP`? Likewise for `RESTART` below?