Extend the GameplayMessageRouter plugin to enable cross-server events

[mikeseese]

The GameplayMessageRouter plugin that comes with Lyra (and shipped with Redwood's plugins under ThirdParty) is a powerful publish/subscribe system that can send arbitrary struct message events keyed off a GameplayTag. It would be neat if we added switch to the publish functions to synchronize the message to all servers (perhaps all shards in the zone and all shards in all zones as two enum options)