Take nEventsPerJob in run_athena.sh from jO instead of commit script

• Move decision of how many events to generate from commit script (https://gitlab.cern.ch/atlas-physics/pmg/mcjoboptions/blob/master/scripts/commit_new_dsid.sh#L207) to run_athena.sh reading from jO
• See if we can/should increase time-out for run_athena job to 2h or 5h (check with CERN IT) (moved to #45 (closed))