Copy the objects in this subset to a new soup while preserving
the relationships between the items in the selection.
Each IndirectObject in the
selection has a unique ID. However the destination soup may already
contain items with this ID. For this reason the process of copying
the objects requires a remapping of old IDs to new ones in the
Some remap entries may already have been created during addition
as the entries in the RemapTypes property get
applied. However most will be created at the point that the CopyTo
method is called. The remap table is accessible via the RemapIDs property.