Allow PacketSet to register ActionStreamPackets with info about their contents

[Jameskmonger]

Currently you have to do this in the PacketSet:

sendGameEvents: ActionStream.ActionStreamPacket;

And then separately you have to bind it up like this:

		call(
			ActionStream.incomingSaga<GameServerToClient.PacketSet, "sendGameEvents">(
				registry,
				"sendGameEvents",
				GameEvents.GameEventActionTypesArray
			)
		),

for incoming, as well as another for outgoing. And repeat for every ActionStreamPacket you use

It would be really nice if this could be automated in some way, even just some kind of incomingStreams(packetSet) or something