new Task subclass: save ROIs

[ne1s0n]

For each ROI (i.e. geom in the dataset lingo, or shape since it comes from the shapefile) save a separate .tiff This task is also useful for preparing training datasets for deep learning.

[ne1s0n]

this could be a new task or an option in the thumbnail task, which generates files like thumb_ROI.png

[ne1s0n]

Done