Visualisation on map canvas: next time step is visualised

[leendertvanwolfswinkel]

This issue exists for the aggregation NetCDF (e.g. Net cumulative discharge), but may also exist for other NetCDF files.

Test data: https://nelenschuurmans-my.sharepoint.com/:u:/g/personal/leendert_vanwolfswinkel_nelen-schuurmans_nl/EVPBIzsxjmxKvVWPOJpGKGEBBHB-6TZ1mpuT5YckukHllQ?e=CbHzgl

This is a bit hard to explain in words, but an image says more than a thousand words:

Another issue is that it would make a lot sense to interpolate between time steps. This should be optional (default = ON). I.e.: