Change shebangs to `#!/usr/bin/env python` instead of
`#!/usr/bin/env python2.7`.

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).

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

six is necessary for making these scripts cross compatible
between python 2.x and 3.x

Changes:
Add six to python_deps.include
Include python_deps.include to all Dockerfile templates in test directory
Include python_deps.include to all Dockerfile templates in stress_test directory
Include python_deps.include to all Dockerfile templates in interop_test directory
Replace print statements with print function calls (from futute..)
Replace .iteritems() with .items() wherever necessary
use six.moves to import BaseHTTPServer
Generate new dockerfiles using generate_projects.sh