All enabled tests are now true unit tests with no external dependencies; new `requirements.txt` file in `test/` that installs testing requirements (`pytest`, `pytest-mock`, etc.); and `run-tests.sh` now has an extra step that installs these

Added run-tests.sh script to each service to run our package tester to enable us
to run unit tests from the cmdline and CI
Refactored makefile's make test script to call run-tests.sh in each image