Coordinate order

[nfahlgren]

Points (backed by matplotlib) uses coordinates in x, y order. get_centroids outputs points in row, column (y, x) order and the napari-based tools also use row, column order.

Whichever convention we use we need to have the tools do the conversion as necessary. The order is easy to flip if needed:

new_coords = [(x, y) for y, x in coords]