Update NuGet metadata to use license expression (#1921)

Build/build.ps1

@@ -13,7 +13,7 @@
   $treatWarningsAsErrors = $false
   $workingName = if ($workingName) {$workingName} else {"Working"}
   $netCliChannel = "2.0"
-  $netCliVersion = "2.1.402"
+  $netCliVersion = "2.1.500"
   $nugetUrl = "https://dist.nuget.org/win-x86-commandline/latest/nuget.exe"
 
   $baseDir  = resolve-path ..

Src/Newtonsoft.Json/Newtonsoft.Json.csproj

@@ -20,7 +20,7 @@
     <PackageTags>json</PackageTags>
     <PackageIconUrl>https://www.newtonsoft.com/content/images/nugeticon.png</PackageIconUrl>
     <PackageProjectUrl>https://www.newtonsoft.com/json</PackageProjectUrl>
-    <PackageLicenseUrl>https://raw.github.com/JamesNK/Newtonsoft.Json/master/LICENSE.md</PackageLicenseUrl>
+    <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PublishRepositoryUrl>true</PublishRepositoryUrl> 
     <RootNamespace>Newtonsoft.Json</RootNamespace>
     <AssemblyName>Newtonsoft.Json</AssemblyName>

Src/global.json

@@ -1,6 +1,6 @@
 {
   "projects": [ "src" ],
   "sdk": {
-    "version": "2.1.402"
+    "version": "2.1.500"
   }
 }