Bugfix for debian defaults and addition of qemu_user and qemu_group

Hi,

I have added the parameters for changing/defining the user ID and group ID for QEMU processes run by the system instance.

Additionally I was not able to define the "default" parameters like you did with the sysconfig-example. "default" is reserved and I have renamed it to "deb_default"

Greetz,
Andre

PS: sorry for the whitespace changes :(