We also add "version" to all docker images and containers
This version is to be incremented manually when we change the shape of the build
image (like changing the golang version or the set of volumes in the data
container). This will delete all older versions of images and containers when
the version is different.
This allows us to start building real dependencies into Makefile.
Leave old hack/* scripts in place but advise to use 'make'. There are a few
rules that call things like 'go run' or 'build/*' that I left as-is for now.