Remove use of main.py and move all customization to settings.txt

[brunyuriy]

The current use of main.py is a poor interface. All customization should instead be in settings.txt. It can be specified exactly the way the five functions (causalDiscrimination(..), groupDiscrimination(..), causalDiscrimination(..), discriminationSearch(..), and getTestSuite()) are described now, but it shouldn't be in a pearl script, it should be in settings.txt. Perhaps you can find a more clean way to specify it there as well.