Instrument AddGroupEntry [Device] [Group] [Position]. Adds [Device]
to the group [Group], at position [Position]. If [Position] is not defined,
the device will be appended.
Usage: Instrument AddGroupEntry [Device] [Group] [Position]
[Device] is the device to be added to the device group.
[Group] is the group name used to define the list of devices.
[Position] is the location to place the device in the device list.