suggest a "clean start" option

[mnfienen]

Suggest an option in the YML file to remove existing files from the sim_ws. I was running into a problem with the original top file being written while debugging some issues. That file was wrong, but even when rebuilding the model from original sources, it was getting read in and thus causing problems. So, suggest a flag to destroy the sim_ws for 100% certainty that all is being written fresh.