Make Creation of gateway.restart gateway.killer File Optional

[simongregorebner]

When starting the gateway binary it always tries to create a gateway.restart and gateway.killer file
This is not so nice (as it produces some error/warning messages on stdout/journald) and is actually not needed if starting the gateway via systemd.
(of course one could set the -home option to /tmp, however these files actually are useless in the systemd scenario)

It would be nice if the creation could be optional and/or there is a option to disable the creation

[ralphlange]

+1
Sounds very reasonable.

Nice Codeathon project for next week!