This MR builds upon !17 (merged), but makes a few minor adjustments, and uses CI to automatically run unit tests.
fslinstaller.py is a stand-alone executable which is never intended to be installed into a python environment or used programmatically, there is no need to have any sort of package structure. So the
fslinstaller.py script has been moved to the project root, and package files have been removed.
Version number also bumped to 3.0.21