The algorithm to compute the nodata mask is now much faster, especially for...

The algorithm to compute the nodata mask is now much faster, especially for datasets with many spectral bands.

Signed-off-by: Daniel Scheffler <danschef@gfz-potsdam.de>
2 jobs for enhancement/speed_up_nodatamask in 1 minute and 22 seconds (queued for 2 seconds)