Implement start, stop and restart methods.

Once we had agreed on the restart logic, the simplest thing to do was to generate the all methods based on that logic.

TODO: Add stop-sleep-start methods.
i don't like this. why isn't this some constant/readonly hash with a mapping for solaris? (imagine doing this for condrestart/try-restart/whateveritiscalledinsolaristhatdoescondrestart) and do a 
```
$op = LINUX_SYSTEMD_OPERATOR{$method} || $method;
```  
(or whatever actual code might be ;); with such a costant for each flavour (`linux_sysv`, `linux_systemd` and `solaris`)