Add copyright headers to dnx script files

Author: dsplaisted

src/Layout/redist/dnx

@@ -1,2 +1,6 @@
 #!/bin/sh
+
+# Licensed to the .NET Foundation under one or more agreements.
+# The .NET Foundation licenses this file to you under the MIT license.
+
 "$(dirname "$0")/dotnet" dnx "$@"

src/Layout/redist/dnx.cmd

@@ -1,2 +1,5 @@
+:: Licensed to the .NET Foundation under one or more agreements.
+:: The .NET Foundation licenses this file to you under the MIT license.
+
 @echo off
 "%~dp0dotnet.exe" dnx %*

src/Layout/redist/dnx.ps1

@@ -1,4 +1,6 @@
-# dnx.ps1
+# Licensed to the .NET Foundation under one or more agreements.
+# The .NET Foundation licenses this file to you under the MIT license.
+
 # PowerShell script to launch dotnet.exe with 'dnx' and all passed arguments
 $scriptDir = Split-Path -Parent $MyInvocation.MyCommand.Definition
 $dotnet = Join-Path $scriptDir 'dotnet.exe'