Use license expression and fix icon

Ix.NET/Source/Directory.build.props

@@ -4,9 +4,9 @@
     <MinClientVersion>2.12</MinClientVersion>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <Authors>.NET Foundation and Contributors</Authors>
-    <PackageIconUrl>http://go.microsoft.com/fwlink/?LinkId=261274</PackageIconUrl>
+    <PackageIconUrl>https://raw.githubusercontent.com/dotnet/reactive/0f837d11385cfaf575861ccc5a5fbcafb22d888f/Rx.NET/Resources/Artwork/Logo.png</PackageIconUrl>
     <PackageProjectUrl>https://github.com/dotnet/reactive</PackageProjectUrl>
-    <PackageLicenseUrl>https://raw.githubusercontent.com/Reactive-Extensions/Rx.NET/master/Ix.NET/Source/license.txt</PackageLicenseUrl>
+    <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)ReactiveX.snk</AssemblyOriginatorKeyFile>