too many levels by default in the CMOR files

The CMOR atmospheric files of the experiment a091 include 62 levels (what is the vertical resolution of EC-Earth V2.3). However, only 16 levels were saved when running this experiment. Such a configuration is very standard, since saving all the atmospheric levels lead to very big files (in particular for EC-Earth 3 that typically has 91 levels). So it would be great that Earthdiagnostic save only the existing levels that has been saved for experiments. In the case of the experiment a091, the 62-16=36 levels of the CMOR files include data equal to zero for T, U, V and P. @rfernand post processed these files with the config file /home/Earth/rfernand/run_earthdiagnostics/a091/diags.conf