Fixing clock type for JWT verifier tool.

Expose per-call host override option in Node

C# code cleanup

Fix debug annotation typo in Python.

Removed "<:" bigram confusing gcc 4.4

Resulted in error:

```test/cpp/end2end/end2end_test.cc:120: error: ‘<::’ cannot begin a template-argument list
test/cpp/end2end/end2end_test.cc:120: note: ‘<:’ is an alternate spelling for ‘[’. Insert whitespace between ‘<’ and ‘::’
test/cpp/end2end/end2end_test.cc:120: note: (if you use ‘-fpermissive’ G++ will accept your code)
make: *** [objs/opt/test/cpp/end2end/end2end_test.o] Error 1```

Use null for default host

Merge pull request #2887 from tbetbetbe/grpc-ruby-default-timeout-of-infinity-will-clearly-not-suprise-most-users

Sets Ruby's default timeout to infinity.

call grpc_init for GoogleDefaultCredentials

Corrects the way the gemspec refers to various files

Document op completion

health checking protocol doc

Adds grpc.primary_user_agent key during stub creation

Exposes call#peer, channel#target

Eliminated some redundant checks in the Node interop client

Move Python protoc plugin tests to grpcio_test.

Set Python user-agent string.

Implement timeout interop test for Python.

Bounds checking for ops in call batch

Added Sandcastle project to generate C# docs

adding node, ruby, and php to cloud to prod interop tests.