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/build.sh

@@ -1,16 +1,17 @@
 #!/usr/bin/env bash
 
-set -x;
-set -e;
+set -xe
 
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-cd $DIR;
 
-cd 1_base/;
-bash build.sh;
+cd $DIR/1_base
+bash build.sh
 
-cd ../2_build/;
-bash build.sh;
+cd $DIR/2_buildpy
+bash build.sh
 
-cd ../3_run/;
-bash build.sh;
+cd $DIR/3_buildwheels
+bash build.sh
+
+cd $DIR/4_run
+bash build.sh