WIP: more work on the docker structure, still not finished with 4_run

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.

docker/2_buildpy/buildpy.docker

@@ -0,0 +1,23 @@
+FROM pillar_base
+MAINTAINER Sybren A. Stüvel <sybren@blender.studio>
+
+RUN sed -i 's/^# deb-src/deb-src/' /etc/apt/sources.list && \
+    apt-get update && \
+    apt-get install -qy \
+        build-essential \
+        checkinstall \
+        curl
+
+RUN apt-get build-dep -y python3.5
+
+ADD Python-3.6.0.tar.xz.sha256 /Python-3.6.0.tar.xz.sha256
+
+RUN curl -O https://www.python.org/ftp/python/3.6.0/Python-3.6.0.tar.xz
+RUN sha256sum -c Python-3.6.0.tar.xz.sha256
+RUN tar xf Python-3.6.0.tar.xz
+RUN rm Python-3.6.0.tar.xz
+
+# To be able to install Python outside the docker.
+VOLUME /opt/python
+
+ENV PYTHONSOURCE=/Python-3.6.0