pyDGS speed on the RPi

[ebgoldstein]

with 1024 x 1024 images, pyDGS is slow on the RPI... pictures take >1 minute to analyze.

One option is to use smaller images for the pyDGS step — for example, by cropping it to be smaller. This might require a new round of optimization of pyDGS params, which can be done using the full suite of 300 images w/ known grain size, skew, and kurtosis...