Change the year number in all cs headers from 2018 to 2019

OpenRA.Mods.Common/Widgets/BackgroundWidget.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2018 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2019 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation, either version 3 of
@@ -71,4 +71,4 @@ namespace OpenRA.Mods.Common.Widgets
 
 		public override Widget Clone() { return new BackgroundWidget(this); }
 	}
-}
+}