Decide how to handle application exit.

Decide how to handle application exit.

When the service exits with exit code n look in
HKLM\SYSTEM\CurrentControlSet\Services\<service>\Parameters\AppExit\<n>,
falling back to the unnamed value if no such code is listed.  Parse the
(string) value of this entry as follows:

    Restart: Start the application again (NSSM default).
    Ignore:  Do nothing (srvany default).
    Exit:    Stop the service.