Implement `RegionDetections` class

[russelldj]

This slightly modifies the initial interface for the region detections class and provides and initial implementation of the methods. The goal is to handle the majority of the boilerplate code in the class and have the user specify the simplest objects.

It also adds a convenience function to convert from a numpy transform matrix to the format expected by shapely.

[russelldj]

I rebased to clean up the nuisance commits from the auto-formatters.

[russelldj]

I refactored the __init__ method to be more flexible. There's still one TODO, but the rest of the logic should be done.