Re-enable automatic SETests, add more unittests, fixes in PrepareOptionsFile
- SETests have been reenabled in the CI environment.
- While testing PrepareOptionsFile, several bugs became apparent (though not 100% sure because the expected behaviour is documented nowhere) that have been fixed,
- Add more unittests for PrepareOptionsFile.
- Started Test/Utilities directory for commonly used test methods, such as to mock the files for a method that opens several files.