MetaDict: Added missing import.
Slot: When resize()ing a multislot, connect the subslots AFTER the size change has been propagated to upstream/downstream partners.
Fixes a bug that can occur in tricky diamond-connection patterns in which subslots would not end up with all the partners that the parent multislot has.
Slot: Propagate UN-ready status through the complete graph before propagating the rest of the meta-state.
This ensures that operators that are about to be totally unconfigured don't ask for upstream values during graph setup.