Properties of cues are now stored in a dictionary and referenced with keys
Cues are now more (but not totally) self-sufficient; that is, they have a weak pointer to their owning workspaces, and they can use it to do things like start and stop themselves.
Cues now implement the up/down push/pull model so that the flow of property data can be controlled more precisely
Workspaces no longer fetch main properties on every update notification
Major changes include: