Fix Pre-Prediction

[cBournhonesque]

• PrePrediction was broken since the introduction of send-side entity mapping.
  That's because:
• client spawns predicted E1 and replicates it to server.
• server spawns E2 and maintains mapping E2<>E1 and replicates it to client
• client spawns confirmed E3 and maintains mapping E2<>E3.

With sender-side mapping, updates related to E2 would be mapped to E1 before being sent.

This PR fixes this problem, and it also works in host-server mode and with hierarchy.

Also fixes:

• the replication_groups example was failing because of a erroneous check in the protocol
• the connect/disconnect systems were running twice (both the normal and the host-server versions were running)
• the server doesn't replicate Spawns to the entity that first spawned an entity.