Enhance pythonpath handling in the script

Allow path passed with a space or egal:
--pythonpath=foo
--pythonpath foo
Enhance reporting when import_class fails
Update print_options "callback" entry if default one (which call jobs run method)
Update worker-config version test
Correct problems passing queue_model/error_model/callback as script argument
Enhance script defaut logging format

And worker logging level set to INFO by default instead of ERROR