add option to run without reanalysis data

[aclerc]

If reanalysis data such as ERA5 is not available but you still want to run wind-up (accepting that northing accuracy will not be checked) there is no easy way to do this. At present I do this by making fake reanalysis data (example: https://github.com/NREL/flasc/blob/main/examples_smarteole/09_wind-up_wake_steering_uplift_analysis.ipynb).

It would be better to add an option to the WindUpConfig that lets you bypass all calculations needing reanalysis data.