Singleton: Attempt to simplify getting the actual singleton ref

[ktoso]

We currently have to perform a dance with "proxy spawns manager, manager spawns the real one".

Thus the obtaining of the ref needs: self.managerRef?.tell(.takeOver(from: from, replyTo: refSubReceive)) and dance with that subreceive.

We should see if we can collapse and simplify those.
The reason this gets tricky is the message protocols, but perhaps we can do something with a CellDelegate there?

[ktoso]

Marked to 0.5 as it's low priority, functionallity does not change much from this. Efficiency does.