Fix the lobby slots.

- lobbyInfo.Slots is now a dictionary, keyed by the name of the PlayerReference that the slot is tied to.
 - LockRace/Color/Team is now specified on the slot, avoiding map lookups in the lobby
 - Observers are no longer tied to slots -> players will join as observers instead of crashing the game if there are no available slots
 - Observers are able to change their name and color

OpenRA.Mods.RA/ServerTraits/PlayerCommands.cs

@@ -71,7 +71,7 @@ namespace OpenRA.Mods.RA.Server
 							return false;
 						}
 						
-						if (server.lobbyInfo.Slots[client.Slot].Spectator)
+						if (client.Slot == null)
 						{
 							server.SendChatTo( conn, "Can't select a spawnpoint as a spectator" );
 							return false;