Add functional tests to tox

This adds functional tests to tox, along with a number of prerequisite
steps. Since this is primarily a bash project, pbr usage has been avoided.
Tests are to be written in python and put in the tests directory.

Running tox -e setupenv will execute a setup script
(tests/setup_docker.sh) to ensure the running instance of docker meets
the minimum version requirement.

Running tox -e images will execute the image building script
(tools/build-all-docker-images) and will parse the resulting output to report
failures.

Running tox -e startenv will generate the environment file, run
"tools/kolla start", and run first time initialization (eventually).

Running tox -e functional is for actually testing the deployed OpenStack
environment via a series of tests utilizing the client APIs.

Change-Id: Iff6dfdca43f0c44d471e7540a7836e56a0de4507