Ditz issue update
Ditz issue update
First draft of SPDX license file creation
Add python-rdflib to README deps

It is needed to create the SPDX license file.
Add SPDX license to dist
Release note: SPDX 1.2 release
Use 'license.spdx' for SPDX license name

Also add 'set -e' to make_dist.sh.
Merge branch 'add-spdx-license'

Add first draft of a SPDX 1.2 license into the distributable, with the
filename "license.spdx".  This requires python-rdflib so add that to the
project dependencies in README.md.

Add 'set -e' to make_dist.sh to better detect errors that might otherwise
silently creep by and break the build.