Added kfold script in util

This is a pretty general kfold script. It basically removes the given values in the given fraction of rows (no randomness in position), of given table. It's usually used as an "after" script with the extractor generating the temporal table to operate on, and with calibration fraction set to zero.

Usually it should be used with a iterative run.sh script, giving different input parameters. If you need the example run.sh and application.conf please contact me.