Look into making coreograph output mask/ROIs rather than physically splitting image #145

Description of feature

Coreograph's output is fragile enough that it might be better to store its output as a non-destructive mask or list of shapes which can be used in downstream analysis after single-cell quantification. One reason for physically splitting cores was to reduce RAM usage for segmentation and quantification as well as improve parallelism, but our tools are improving in these areas.