Nebulous: Implemented a number of bug fixes and modifications to
ensure no loss of data.
Each volume can now be associated into a cabinet, defining their
physical arrangement.
File creation: new files without a specified volume are created
on a random volume from a subset of the N least full.
Replication: file replication uses the same volume selection
method, with the constraints that a copy not be automatically
placed on the same volume as another, and that the first copy
not be housed within the same volume.
Cull: instead of removing the first available instance, first
attempt to remove an instance on the same volume as another,
then attempt to remove an instance in the same cabinet as
another, and then remove the first only if those fail.
Corrected bug that prevented the deletion of an object if it had
more than one unavailable instance.
Fixed nebdiskd to synchronize between volume->mountedvol tables
and to properly remove volumes that were no longer accessible.