output native suite2p segmentation file

[mattjdavis]

Feature request

We would find it useful to have the 'stat.npy' file that suite2p generates during roi segmentation, in order to load the rois into the suite2p gui for review. Possibly the 'iscell.npy' if that is generated as part of the segmentation output.

output file descriptions:
https://suite2p.readthedocs.io/en/latest/outputs.html