SSA-6324: refactored prop setter for testability and created tests; added script to run all tests in data repo

SSA-6324: datafetcher tests proceed as expected in IJ and at command line, but not in Docker container. scode_updater tests proceed as expected in IJ, but not at the command line or in Docker container. Requirements updated; convenience script added for rebuilds.

Implemented parsing of setup.py files within a buildout recipe; next is to generate meta.yaml files for each setup file parsed

SSA-6324: All tests pass when run locally. In Docker container, tests that exercise the CLI all fail, unable to find the "datafetcher" entry_point.

SSA-6324: tests pass when run locally; some fail in Docker container. Committing what I've got so as not to lose it after tearing my hair out for a day and a half.

SSA-6324: placate Pylint somewhat; this time -really- get rid of the properties file after the Docker image is built; look what Pathlib can do!

SSA-6324: pytest on datafetcher_test.py executes in a Docker container. capo properties file is copied to the docker build directory, then deleted.

Tests all succeed when executed in IJ.