Implementation of divergence method by FMI.

Add class SMARTCARB Dataset to init Level-2 with uncertainty scenario and constellation that can be used by divergence method to laziliy request datasets for next date. Adding a similar class for other satellites makes method indepdent from SMARTCARB dataset

Unmix plumes

Rewrite cross-sectional flux method (and add support for reading TROPOMI data)

Fix coco2 dims and other bugs