fixed #21: Data source does not show default 
https://github.com/oerich/ReqtDisc/issues/issue/21
fixed #76: Allow using seeds for k-fold cross validation 
https://github.com/oerich/ReqtDisc/issues/issue/76

Now I only allow a Random instance in Util. There, I can set the random
seed centrally. It seems like the results are not exactly the same,
though.