Merge pull request #1053 from jtattermusch/csharp_metadata

src/csharp/Grpc.Core.Tests/ClientServerTest.cs

src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj

...p/Grpc.Core.Tests/Internal/MetadataArraySafeHandleTest.cs

src/csharp/Grpc.Core/Call.cs

src/csharp/Grpc.Core/Calls.cs

src/csharp/Grpc.Core/Grpc.Core.csproj

src/csharp/Grpc.Core/Internal/AsyncCall.cs

src/csharp/Grpc.Core/Internal/CallSafeHandle.cs

src/csharp/Grpc.Core/Internal/MetadataArraySafeHandle.cs

src/csharp/Grpc.Core/Marshaller.cs

src/csharp/Grpc.Core/Metadata.cs

src/csharp/Grpc.Core/ServerServiceDefinition.cs

src/csharp/Grpc.Core/Stub/AbstractStub.cs

src/csharp/Grpc.Core/Stub/StubConfiguration.cs

src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs

src/csharp/Grpc.Examples/MathGrpc.cs

...rp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj

src/csharp/Grpc.IntegrationTesting/TestServiceGrpc.cs

src/csharp/ext/grpc_csharp_ext.c