Update read_dat.py
Update read_dat.py

streamline and improve the code for finding fmax frame, and add device to filename for images saved with debug set to "print"

danforthcenter/plantcv,stiphyMT/plantcv,danforthcenter/plantcv,danforthcenter/plantcv,stiphyMT/plantcv,stiphyMT/plantcv