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

OpenRA.FileFormats/Exts.cs

@@ -171,5 +171,10 @@ namespace OpenRA
 			++v;
 			return v;
 		}
+
+		public static string JoinWith<T>(this IEnumerable<T> ts, string j)
+		{
+			return string.Join(j, ts.Select(t => t.ToString()).ToArray());
+		}
 	}
 }

OpenRA.FileFormats/FieldLoader.cs

@@ -330,7 +330,7 @@ namespace OpenRA.FileFormats
 			if (f.FieldType.IsArray)
 			{
 				var elems = ((Array)v).OfType<object>();
-				return string.Join(",", elems.Select(a => a.ToString()).ToArray());
+				return elems.JoinWith(",");
 			}
 
 			return v.ToString();

OpenRA.FileFormats/MiniYaml.cs

@@ -228,7 +228,7 @@ namespace OpenRA.FileFormats
 			if (throwErrors)
 			if (noInherit.ContainsValue(false))
 				throw new YamlException("Bogus yaml removals: {0}".F(
-					string.Join(", ", noInherit.Where(x => !x.Value).Select(x => x.Key).ToArray())));
+					noInherit.Where(x => !x.Value).JoinWith(", ")));
 
 			return ret;
 		}
@@ -271,7 +271,7 @@ namespace OpenRA.FileFormats
 
 		public static string WriteToString(this MiniYamlNodes y)
 		{
-			return string.Join("\n", y.ToLines(true).Select(x => x.TrimEnd()).ToArray());
+			return y.ToLines(true).Select(x => x.TrimEnd()).JoinWith("\n");
 		}
 
 		public static IEnumerable<string> ToLines(this MiniYamlNodes y, bool lowest)

OpenRA.FileFormats/Primitives/Bits.cs

@@ -57,7 +57,7 @@ namespace OpenRA.FileFormats
 
 		public override string ToString()
 		{
-			return string.Join(",", BitAllocator<T>.GetStrings(Value).ToArray());
+			return BitAllocator<T>.GetStrings(Value).JoinWith(",");
 		}
 
 		public override int GetHashCode() { return Value.GetHashCode(); }