Add file copyright

src/DotNetCore.CAP/BrokerConnectionException.cs

-using System;
+// Copyright (c) .NET Core Community. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using System;
 
 namespace DotNetCore.CAP
 {

src/DotNetCore.CAP/ICapTransaction.Base.cs

-using System.Collections.Concurrent;
+// Copyright (c) .NET Core Community. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using System.Collections.Concurrent;
 using System.Threading;
 using System.Threading.Tasks;
 using DotNetCore.CAP.Persistence;

src/DotNetCore.CAP/Messages/Headers.cs

-namespace DotNetCore.CAP.Messages
+// Copyright (c) .NET Core Community. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+namespace DotNetCore.CAP.Messages
 {
     public static class Headers
     {

src/DotNetCore.CAP/Messages/Message.cs

-using System;
+// Copyright (c) .NET Core Community. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using System;
 using System.Collections.Generic;
 using JetBrains.Annotations;
 

src/DotNetCore.CAP/Messages/TransportMessage.cs

-using System;
+// Copyright (c) .NET Core Community. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using System;
 using System.Collections.Generic;
 using JetBrains.Annotations;