Add option to prevent unexpected empty icb restart
Context
Rebuilt icb restart is a 2 stages process: rebuilt the 2d variables (rebuild_nemo) then the icb positions (icb_combrest.py). If you forgot the second stage, NEMO restarts without any trouble BUT with no iceberg.
Proposal
Add an option ('-i' for example) in rebuild_nemo to trigger icb_combrest.py automatically within rebuild_nemo after the stage 1 (rebuilt of 2d variables).