add IEnum<T>.JoinWith, use it to clean up a bunch of things

OpenRA.Game/Game.cs

@@ -280,7 +280,7 @@ namespace OpenRA
 
 			// Discard any invalid mods
 			var mm = mods.Where( m => Mod.AllMods.ContainsKey( m ) ).ToArray();
-			Console.WriteLine("Loading mods: {0}",string.Join(",",mm));
+			Console.WriteLine("Loading mods: {0}", mm.JoinWith(","));
 			Settings.Game.Mods = mm;
 			Settings.Save();
 

OpenRA.Game/GameRules/ActorInfo.cs

@@ -102,8 +102,8 @@ namespace OpenRA
 				else if (++index >= t.Count)
 					throw new InvalidOperationException("Trait prerequisites not satisfied (or prerequisite loop) Actor={0} Unresolved={1} Missing={2}".F(
 						Name,
-						string.Join(",", t.Select(x => x.GetType().Name).ToArray()),
-						string.Join(",", unsatisfied.Select(x => x.Name).ToArray())));
+						t.Select(x => x.GetType().Name).JoinWith(","),
+						unsatisfied.Select(x => x.Name).JoinWith(",")));
 			}
 
 			return ret;

OpenRA.Game/Group.cs

@@ -36,7 +36,7 @@ namespace OpenRA
 		{
 			/* debug crap */
 			Game.Debug("Group #{0}: {1}".F(
-				id, string.Join(",", actors.Select(a => "#{0} {1}".F(a.ActorID, a.Info.Name)).ToArray())));
+				id, actors.Select(a => "#{0} {1}".F(a.ActorID, a.Info.Name)).JoinWith(",")));
 		}
 
 		/* todo: add lazy group path crap, groupleader, pruning, etc */

OpenRA.Game/Map.cs

@@ -343,7 +343,7 @@ namespace OpenRA
 				if (!OpenRA.Rules.TileSets.ContainsKey(Tileset))
 					throw new InvalidOperationException(
 						"Tileset used by the map ({0}) does not exist in this mod. Valid tilesets are: {1}"
-						.F(Tileset, string.Join(",", OpenRA.Rules.TileSets.Keys.ToArray())));
+						.F(Tileset, OpenRA.Rules.TileSets.Keys.JoinWith(",")));
 
 				// Tile data
 				for (var i = 0; i < MapSize.X; i++)

OpenRA.Game/Orders/UnitOrderGenerator.cs

@@ -37,7 +37,7 @@ namespace OpenRA.Orders
 			if (actorsInvolved.Any())
 				yield return new Order("CreateGroup", actorsInvolved.First().Owner.PlayerActor, false)
 				{
-					TargetString = string.Join(",", actorsInvolved.Select(a => a.ActorID.ToString()).ToArray())
+					TargetString = actorsInvolved.Select(a => a.ActorID).JoinWith(",")
 				};
 
 

OpenRA.Game/Widgets/WidgetUtils.cs

@@ -203,7 +203,7 @@ namespace OpenRA.Widgets
 					else
 						break;
 				}
-				return string.Join("\n", newLines.ToArray());
+				return newLines.JoinWith("\n");
 			}
 			return text;
 		}