Stop checking IsLoggingOut on these listeners, if called with a root agent then we always want to perform these actions.
This covers cases where the client is closed due to manual kick, simulator shutdown, etc.
This means that avatar/appearance data of other avatars and scene objects for a client will be sent after the ack rather than possibly before.
This may stop some avatars appearing grey on login.
This introduces a new OpenSim.Framework.ISceneAgent to accompany the existing OpenSim.Framework.ISceneObject and ISceneEntity
This allows IClientAPI to handle this as it can't reference OpenSim.Region.Framework.Interfaces