Every subject this session can make claims about: the core's path, then
the backend's. Two registrations of one name are one subject, each
answering its own properties (ChRIS adds tags to path).
Returns Map<string,SubjectEntry>
The subjects, by name, in the order they were registered.
Every subject this session can make claims about: the core's
path, then the backend's. Two registrations of one name are one subject, each answering its own properties (ChRIS addstagstopath).