`test_net_rop_ddCi` was updated to use and account for reaction orders
appropriately. Many updates to docstrings and comments. Typo fixes.
usesCoverageDependence was also implemented in a more generic manner
so it can be extended to other reaction types.
The import time for pkg_resources is significant. As of Python 3.8, the
two commands we use can be replace by 'importlib.metadata.version' and the
lighter-weight 'packaging.version.parse'.
