Fix logger issue

[mschwoer]

• Fixes the followiung issue on python < 3.11:

  
  0:00:00.027515 INFO:                 │   └──mobility_observed 
  0:00:00.027580 INFO:                 └──output_columns
  0:00:00.027647 INFO:                     └──mobility_calibrated 
  0:00:00.029549 INFO: Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/alphadia/cli.py", line 333, in run
  plan = Plan(
  File "/usr/local/lib/python3.9/site-packages/alphadia/planning.py", line 128, in __init__
  if (level_code := logging.getLevelNamesMapping().get(level_to_set)) is None:
  AttributeError: module 'logging' has no attribute 'getLevelNamesMapping'

0:00:00.029638 ERROR: module 'logging' has no attribute 'getLevelNamesMapping'

`getLevelNamesMapping` is available for python >=3.11 only.

 Note that I also changed the behaviour: if the requested log level is not available, an error is raised. Alternatively, one could just continue with the default level.

- exit on error with a nonzero exit code
- fix a little flaw that filenames in log output had a trailing dot