SpaceManager is, in essence, ManagedTables on the disk.
Instead of providing an array of pointers to tables, it
provides an Ordered Collection of disk-based Objects, in
our case stored in ObjectFiler format.  

The underlying design is just managed tables: an array of
integers representing file addresses.  At each file position,
find the beginning of the ObjectFiler object.

To access a given object, send objectInSpaceNumber:, which
just positions the file and invokes ObjectFiler to instantiate
the object.

SpaceManager is given a pretty face in the VirtualDictionary,
part of DictionaryStack.

(RonJeffries)