Salmagundi

- Add method Config.as_dict() in module config
- Add exception DuplicateError in module config
- Options can now be added to sections in module config (renamed parameter name -> key)
- Add a tag to specification in module config
- Bugfix: Config.\_\_delitem\_\_() now works even if create_properties=False

- Add function convert_string() to module config
- Add class StopWatch to module utils

- Add parameter numeric to config.convert_loglevel()

- Change utils.ensure_single_instance(): parameter lockfile -> lockname

- Bugfix: utils.ensure_single_instance()

- Add functions sys_exit() and ensure_single_instance() to module utils
- Add parameter err_code to utils.docopt_helper()