added NuGet package specifications

src/csharp/Grpc.Core/Grpc.Core.nuspec

+<?xml version="1.0" encoding="utf-8"?>
+<package >
+  <metadata>
+    <id>Grpc.Core</id>
+    <title>gRPC Core</title>
+    <summary>Core C# implementation of gRPC - an RPC library and framework</summary>
+    <description>Core C# implementation of gRPC - an RPC library and framework. See project site for more info.
+     This is an experimental release, not ready to use.
+    </description>
+    <version>0.1.0</version>
+    <authors>Google Inc.</authors>
+    <owners>jtattermusch</owners>
+    <licenseUrl>https://github.com/grpc/grpc/blob/master/LICENSE</licenseUrl>
+    <projectUrl>https://github.com/grpc/grpc</projectUrl>
+    <requireLicenseAcceptance>false</requireLicenseAcceptance>
+    <releaseNotes>The first experimental release. Not ready to use.</releaseNotes>
+    <copyright>Copyright 2015, Google Inc.</copyright>
+    <tags>gRPC RPC Protocol HTTP/2</tags>
+  </metadata>
+  <files>
+    <file src="bin/Release/Grpc.Core.dll" target="lib/net45" />
+  </files>
+</package>

src/csharp/Grpc.nuspec

+<?xml version="1.0" encoding="utf-8"?>
+<package >
+  <metadata>
+    <id>Grpc</id>
+    <title>gRPC</title>
+    <summary>C# implementation of gRPC - an RPC library and framework</summary>
+    <description>C# implementation of gRPC - an RPC library and framework. See project site for more info.
+     This is an experimental release, not ready to use.
+    </description>
+    <version>0.1.0</version>
+    <authors>Google Inc.</authors>
+    <owners>jtattermusch</owners>
+    <licenseUrl>https://github.com/grpc/grpc/blob/master/LICENSE</licenseUrl>
+    <projectUrl>https://github.com/grpc/grpc</projectUrl>
+    <requireLicenseAcceptance>false</requireLicenseAcceptance>
+    <releaseNotes>The first experimental release. Not ready to use.</releaseNotes>
+    <copyright>Copyright 2015, Google Inc.</copyright>
+    <tags>gRPC RPC Protocol HTTP/2</tags>
+    <dependencies>
+      <dependency id="Grpc.Core" version="0.1.0" />
+    </dependencies>
+  </metadata>
+</package>