Check number of files in gridpack

The number of files in a gridpack shouldn't exceed 80k, otherwise some grid sites will crash. This has happened a number of times recently, e.g. for the FxFx job where the gridpack contained several files per Feynman diagram. MadGraph control cleans up logs and .o files in the latest release, but for older releases it would be good to have a dedicated pipeline step that throws an error if the number of files in the gridpack is larger than 80k. Probably something like tar -ztvf *.tgz *.tar.gz could work?