C# client side support for TLS

A couple of fixes + a test for client side authentication of hostnames

adding C# support to gce_setup scripts

added C# to run_tests.py

Solving crashes in async tests

Add a macro to control the string and protobuf::Message typedef.

Allow only one thread to complete ioreqs at once

Polishing C# Dockerfiles

- correctly trigger done_cb to avoid stuck requests
- pass up an UNAUTHENTICATED status so that clients know what happened

adding a build images script and remove some tests while investigating t...

Otherwise we can get a total-queue-ordering violation and complete some
ioreqs out-of-order. This leads to events being pushed to the completion
queue out-of-order, and that leads to applications believing streams are
completed before receiving the last message.

Fix backslash line endings for grpc_python/Dockerfile.

Without the correct line endings docker had errors interpreting '&&' as a command.

Remove some debugging logs from the unary poll promote path

Update pubsub example channel creation and credentials. This is a duplicate of #817.

Propagate grpc_google_default_credentials_create errors

Adding a Travis badge.

Now setup as a driver and N anonymous workers that may become clients or servers.
Will convert async soon.

Revert "dockerfiles/go: go install from GOPATH and remove bash from CMD"