Pins all the build dependencies required by poetry, otherwise
poetry installs arbitrary versions of them, which leads to a wrong
version of cryptography being installed and the build failing.
Note that Cloud dependencies (pillar and the like) has to have their
build dependencies pinned in the same exact manner, for the same reason.
Pins all the runtime dependencies as well, because Cloud can only use
poetry==1.0 due to its source dependencies, so there's no
"poetry lock --no-update" and each "poetry lock" updates arbitrary packages.
WHEELHOUSE: since we're defining the variable we might as well use it.
DOCKER_IMAGE_NAME: introduced to prevent duplications of the name, and to
add a little confirmation message when the script is done.
Because we only pushed the final image to Docker Hub, it was impossible to
pull the base image someone else created and "quickly" build a new deploy
image.
Now the deploy scripts push (some) of the intermediate images as well,
making it possible to pull them later. I've added `build-pull.sh` and
`full-pull.sh` to perform this pull and built up from the pulled images.
1_base: builds a base image, based on Ubuntu 16.10
2_buildpy: builds two images:
2a: an image that can build Python 3.6
2b: an image that contains the built Python 3.6 in /opt/python
3_buildwheels: builds an image to build wheel files, puts them in ../4_run
4_run: the production runtime image, which can't build anything and just runs.
