Get simpler dependency than full-blown Fiji / ImageJ for ROI functionality

We use `RoiDecoder.openFromByteArray` to read ZIPped ROI files, and `roi.containsPoint` to filter spot centers ("points") for inclusion in nucleus ("roi"). These are relatively simple tasks that shouldn't require full-blown (including GUI) Fiji / ImageJ. This would allow us to also simplify our `build.sbt` related to logging setup -- see #4 