Tests all succeed when executed in IJ.

SSA-6325: a few import and path tweaks were necessary to get all the tests to run from the command line

master: reorganized datafetcher "SDM-only" functionality removed. All tests pass, including those that launch DF from a process to simulate command-line execution. TODO: actual command line, as below, should work but doesn't yet:

datafetcher --profile local --output-dir ~/Downloads --product-locator uid://evla/execblock/93e1c0cd-76de-4e65-a3f2-d5fe55f386d8 --verbose

Pylint also finds some errors, the consequence of fixing which puts red ink in the IJ editor and causes the above-mentioned command-line tests to fail.