speed up production if multiple buildings of the same type exist

OpenRA.Mods.RA/Production.cs

@@ -22,6 +22,9 @@ namespace OpenRA.Mods.RA
 	{
 		public readonly string[] Produces = { };
 
+		public readonly float SpeedUp = 0;
+		public readonly float MaxSpeedUp = 0;
+
 		public virtual object Create(ActorInitializer init) { return new Production(this); }
 	}