Add a config option to murmur.ini to set superuser password

I compiled 1.3.x from git - wanting to set a superuser password requires to annoyingly launch murmur manually with a parameter.

I'd welcome an option to set superuser option via a config line in murmur.ini.

https://wiki.mumble.info/wiki/Murmurguide#Linux_4

If there are other ways to set the superuser password then they are not noted in the wiki.

EDIT: Looks like the superuser password is autogenerated at first start of the server and is in logs. Would still welcome a config option tho.