Commits
CAS-13085: added check_mslist() method to cleanhelper.py and added
a call to it in task_concat.py (also as a demo for other tasks). The method returns a dictionary which is empty if all MSs in the input list have a consistent setup. In the case of concat, there will now be a warning message if the check_mslist return value is not =={} saying that the concatenation may fail.