Embed scripts/*.py in HistomicsTK / girder

[Leengit]

Make SuperpixelSegmentation.py, FeatureExtraction.py Predict.py also work within the context of girder / HistomicsTK. In particular allow them to get their inputs from and write their outputs to girder.

This might be achieved by emulating HistomicsTK/histomicstk/cli/SuperpixelSegmentation.py. Don't forget to output centroid information too. As a short cut, can we download from girder only if the data are not already present? Consult with David about whether this is too much data for girder -- including whether all input SVSs from the biologists would be stored there too.