Dockerized python - poetry image

This is a base (onbuild) image of the python docker image. This build adds the following improvements:

• Default installation of poetry with virtualenvs.create set to false (No virtual environment will be built).
• Installation of the Google cloud DB proxy app.
• On build of poetry install

Python version builds

Setting a docker build-arg results in additional python build versions. For example the following command will build a python3.8 image:

The default build if left blank is currently set to python 3.7.7

docker build -t test:latest-onbuild --build-arg=PYTHON_BUILD_VERSION=3.8 .