WIP: Derive UUIDs of embedded AVMs from UUIDs of parent AVM and feature.
WIP: Derive UUIDs of embedded AVMs from UUIDs of parent AVM and feature.

- Extract code that handles disconnecting feature from value and
  deleting value (if feature is complex) into two separate methods.

itsjeyd/ODE,itsjeyd/ODE,itsjeyd/ODE,itsjeyd/ODE