Make the variable names in SOIT self-consistent

[danielmwatkins]

SOIT expects inputs of centroid_x and centroid_y. As written, this really is centroid_lat and centroid_lon. The use of x and y here is ambiguous at best, but really is quite misleading because latitude is not an x coordinate in most map projections. I suspect but am not sure that there could be errors with some parts of the code expecting x and y to be polar stereographic and SOIT expecting latitude longitude.

It also forces lat/lon into integer, which means that the location can be nearly 100 km away from the correct centroid.

[danielmwatkins]

To add to this: I'd like to be clear throughout on the use of lat/lon versus x/y. I imagine that the best way to do this would be to have the flow generator be the place that has the if/then with the crs, translating whatever choice the user made into the terms needed in the rest of the script.

[danielmwatkins]

This has mostly been fixed - last thing is to adjust the docstring for pass times cylc.