(The time-related first part of it, anyway.)

Setuptools was updated and our hacky namespace-package-chickens came
back to roost. This removes the unsupported namespace package hacks.

Some features relating to proto2 extension querying are missing due to
missing upstream features required to support them (see
https://github.com/google/protobuf/issues/2248).

Also change grpcio-tools to be a runtime dependency of grpcio-tests,
grpcio-tools is run as part of the tests.

-Rename namespace to grpc_health->grpc to match spec
-Proper use of NOT_FOUND status code
-Improve testing
-Add source distribution to artifact build

Moves all tests into a separate package. This does not change existing
supported means of running tests (e.g. through run_tests.py).

(1) Move dependency on protobuf from grpcio to grpcio_test. While the
most-commonly-foreseen use case of grpcio makes use of protobuf,
technically protobuf is not strictly needed and there's no actual
in-code relationship between grpcio and protobuf.

(2) Loosen the dependency on protobuf from ==3.0.0a3 to >=3.0.0a3.

(3) Update all references to 0.10.0* to 0.11.0.

(4) Alphabetize the grpcio_test dependencies.

Adds the initial reference implementation for health-checking in gRPC
Python as a separate project (but within the same grpc package to keep
namespaces consistent). Only installs the package to test the
build-proto-modules custom command introduced in the health-checking
project.

Also updates the version of grpcio_test. Now that grpcio and its tests
are in different project packages, the version numbers should be kept in
sync.

This is in preparation of moving all tests into a separate package to
enable ease of coverage checking and testing.

Conflicts:
	src/python/src/setup.py

Also adds the commands to the grpc_docker shell library script to
support running in docker.

The server_host_override flag's implementation remaining
outstanding means that this only works over insecure
connections for now.

The source code is moved from src/python to
src/python/src. A setup.py is added at
src/python. The build_python.sh and
run_python.sh scripts are updated to build
and run the Python tests by building a
package and installing it in the developer's
Python 2.7 virtual environment.

It's rather unimpressive at the moment with just
one module.