Hitfinding does not play well with updates to droplet analysis

[rribson]

XES analysis hitfinding currently does not work with droplets. I believe it's because of naming (hit finding is looking for "epix" attr in spectroscopy run object, "epix_ROI" is assigned earlier w/ recent changes. I will try to make this compatible and check that it is working for these cases:

1. using droplets + multiple ROI's
2. using droplet + constructing full detector image
3. not using droplets + using import ROI
4. not using droplet + no import ROI