skytools.scripting: added shutdown() to BaseScript
skytools.scripting: added shutdown() to BaseScript

This should be used for cleanup code instead of abusing stop(),
which is called from signal handler.

markokr/skytools,tarvip/skytools,markokr/skytools,overdrive3000/skytools,tarvip/skytools,tarvip/skytools,markokr/skytools,overdrive3000/skytools,overdrive3000/skytools