Ghost Actors can manage Sub Actors

[neonphog]

PR summary

Removes the awkward Inflator concept in favor of private "DeepRefs" and GhostActorSystem refs that know how to "plant" things with your local context.

Review checklist

• [ ] The story has unit or integration tests
• [ ] No new bugs, and any tech-debt is identified and justified
• [ ] There is enough API documentation (how to use)
• [ ] There is enough code documentation (how the code works)