RegisterVolumeGroup:
PROCEDURE [volumeGroupID: YggEnvironment.VolumeGroupID, volumes:
LIST
OF YggEnvironment.VolumeID];
TEMPORARY (until we figure out how this should really be done...)
Registers a volume group consisting of the specified volumes. Must be called after Initialize and before any operation that specifies a VolumeID or VolumeGroupID (AlpineFile.Open, AlpineFile.Create). Fatal error if volumeGroupID or any of volumes has already been registered.